Clive: I know we are behind the times here in the USA, but hospitals use a ton of fluorescent lamps mostly in offices, hallways and stairwells, especially if the area hasn't been remodeled or updated in many years. Most fixtures use compact fluorecscents and rarely LED, but that is slowly changing to LED "strip" lamps and some four foot drop in retrofit LED lamps that don't require the ballast being removed, as a side note about 20 years ago a hospital I worked in did a "retrofit" of the fluorescent fixtures from a T-12 lamp to T-8 lamp and removing the old magnetic ballasts (many of them were of the potted type some with PCB's.) to an electronic ballast. The new electronic ballast were capable of dual input voltages (120 or 277 volt). Imagine how many fixtures could be run on one 277 volt, 20 amp circuit! Oh, and the operating theatres were notorious for six lamp-four foot fluorescent lamps, Because the operating rooms almost never were remodeled unless being changed to a different configuration for new equipment or procedures, the operating rooms are large source of revenue for a hospital and to shut a room down and do the infection control/dust mitigation was kind of big money. -John
Wiring a newly built hospital in the us four years ago and general contractor chose the cheaper option for lighting. All fluorescent fixtures in a brand new hospital just blew my mind
I was electrical maintenance in the '90s at a hospital...we were slowly replacing the older magnetic ballasts with electronic ones ( as magnetic ones failed, they were replaced with newer electronic ones) The old magnetic ones would have " earwax" running out of them sometimes when they failed. We didn't shut the power off when replacing ballasts! Really couldn't. I always installed a AG-3 fuse and holder in line to make it easier for the next guy... You're right...they didn't want to shut down the OR for anything. I had to replace a 24volt, 35 amp transformer that powered the surgical lights...took a few hours ( difficult location), I got chewed out because some estimate said it only took 45 minutes...I believe this hospital had around 3000 florescent fixtures ..
Same here in Brazil. We still have some surgery lights that use incandescent bulbs, as an example of how they sometimes prefer to not updated to new tech if it's working.
@@Bleats_Sinodai a lot of dentists still use incandescent/halogen lights because they have the reflectors that reflect most visible light, but pass infrared so heat goes the opposite direction of the light output (much like some 50W MR/GU halogen lights).
There are a lot of fluorescent lights in many old buildings all over Europe too. My office even has a fluorescent light that is so old the tubes for it aren't sold anymore.
Thanks for the video. Not that long ago, flourescent tubes were used for lighting in pretty much every school and office building in my part of the world. Nowadays, they have mostly switched to LED panels. What I hate about modern LED lamps is that they are often deliberately built not to last long (especially the cheaper ones). Manufacturers tend to overdrive the LEDs a lot to squeeze more light out of a smaller number of diodes causing them to die early. And often the death of a single LED package kills the entire light because they are wired in series.
I'm going to continue to use fluorescent lighting in my home and have stocked up on fluorescent tubes and other spares. As a toddler in the 70s they fascinated me, the way a tube could light so brightly and evenly. Was always also fascinated by the different start up behaviours. In 1978, only a few weeks after starting school, long thin boxes with purple text were delivered to the school which contained 8ft Thorn pop packs. These were to replace tungsten lighting. Still remember as the winter months took hold how well these lights lit the room, they had what was at the time cutting edge lighting technology in the form of 100w Krypton tubes.
Just don't get/stay too close to them, I used to use em as a UV source for curing UV solder mask, etc. The sun was also good, but well, this being Ireland, its rarer than dinosaur farts 😀 Now I use a dedicated UV source, but you get the idea.
"Quite irrelevant, because . . . . Who uses fluorescent tubes these days?" Well, some months ago, I was reverse-engineering a four-little-fluorescent-tubes bulb circuit (more complex but also more compact than this in the video) and one part of the push-pull circuit made no sense to me, it seemed to be reversely fed. Your explanations have been very relevant for me to understand how it worked! Thanks a lot!
@@bigclivedotcom No, it was just a light bulb. I've just retrieved it from a drawer and realised it's just two, not four, but U-shaped, tubes, inter-communicated via a short (4 mm.-long) transversal tube. Branded IKEA, model no. 2P211. Specs: 220-240V, 96 mA, 50-60Hz, 11W, 600 lumen. Made in China.
Here in the US, electronic ballasts are pretty simple things--many times even simpler than the unit described. Very often, the tube heaters are not used at all--both sides of the tube heater are tied together and only a single wire goes to each end of the tube. I've got a pile of old General Electric Industrial 32/40 watt 120V ballasts that date back to the late 80s and they work just this way. The nice thing about electronic ballasts is that they're very light when compared to the old iron-core ones--a benefit when you're retrofitting ceiling-mounted fixtures.
I still run fluorescent because I like it! On magnetic chokes too. The extra warmth helps heat the house most of the year anyway. That ballast doesn’t have any tube end-of-life shutdown, so be prepared for cracked glass and melting lampholders if a tube fails and the ballast keeps driving it!
the full wave rectifier is actually constructed with series capacitors to allow easy conversion to 115V input, just populate the "BX" position with a jumper and it will become a doubler-rectifier. That's also the reason for the center tap going to the lamp.
That was my first guess as well but stupidly that's not the case. From what I can see on the board photos both ends of "BX" are actually connected together.
@@eDoc2020 Yeah, but its a very easy and reasonably safe trace to cut to separate them. (I thought that position might be for a ferrite bead, so I paused the video there and spent a second staring at it. It looked like it was designed to be cut, but I couldn't figure out why you'd want to do that. This is a much better explanation for that footprint. I feel slightly dumb for not recognizing what you guys did.)
(To preface, I posted this comment on the day you made this video public, and it somehow ended up in the comment section of some random RUclips short (found out when I got a very confused sounding reply from someone), so I guess RUclips is broken, this out of the way)-Very cool to see how these electronic ballasts work. Also ironic that you uploaded this because I actually just converted one of my fluorescent fixtures from electronic to magnetic preheat ballast haha. Electronic ones are good and all, but they are really rough on the tubes, the old preheat ballasting systems were much more gentler when it comes to starting up the lamp, pretty important with my fixture since all my tubes are vintage, in fact I have a Sylvania tube that dates back to 1952! (this one actually happens to be an F8T5 type tube that I found in a vintage manual preheat desk lamp, which explains why the tube is still old and still works!) I’ve also always liked the Blinky startups 😉
fluorescent lights and gas discharge tube devices in general are incredible. sort of sad, but also understandable seeing them slowly being phased out. it’s a bit silly. theoretically a perfect fluorescent light could last more than the lifetime of a human being and much longer in ideal conditions. but of course we live in the real world, so achieving a perfect light or perfect conditions is impossible, but still, they we’re able to last long without it just being a stroke of luck. with proper setup they were reliable and durable. but then came CFLs. oh boy. we wanted the luxury of using our good ol’ edison sockets and having all the benefits of the reliability and durability of big fluorescent tubes. turns out sticking a high voltage ballast into the space of a golf ball with extremely limited airflow isn’t as easy as it sounds (well it doesn’t even sound easy, but you know what i mean). so they broke. the more they broke the more people expected them to break, and the more people expected them to break the more manufacturers turned to making cheap, but replaceable bulbs rather than making then a bit expensive, but long lasting. all of this sounds waaay too familiar. LEDs anyone? i didn’t expect to write an essay, but here we are lol. don’t get me wrong, i love leds, but i think we have become way too lenient when it comes to things breaking. and the more lenient we become, the more things will inevitably break
My favorite has discharge lamps all use metal salts and a very hot arc, 1000 watts of limited band orange light is so lovely, reminds me of sweet home Chicago, you can always find your bearings just by looking up at the clouds and finding the orange glow, sadly the glow isn't as orange anymore because of the trend for LEDs replacing them, i still want a low pressure sodium lamp.... Never got my hands on 1
@@frogz I'm young enough to only recall seeing low pressure sodiums in my early childhood, but i kinda miss them everytime i see picture of them lighting up a street in pure yellow cancelling all other colors.
We shouldn't feel bad about writing more online. Your comment is maybe one page in a novel. Social media has made people lazy. We're having interesting discussions here. The fact that it fills up a small smart phone screen or a comment box on a computer deceives the mind, it really isn't very much to read at all.
I have seen abandoned buildings still powered here on RUclips. Many of those are the old magnetic ballasts, and they sem to last forever. There was one place that was decayed so much that things were falling out of the ceiling. Most of the hallway lighting was still working 20 years after the place closed to the public for the final time. This place was built in the thirties if I remember right. The newer electronic ones (mostly) seem pretty good too. There was another video I saw of a small abandoned strip mall that was still powered. A small general store (Think Dollar General, but it wasn't that.) had power still and a few lights were still on, but flickering. There was a TRUE reach in display fridge that was still working fully, Keeping temperature, sounded good and one of the fluorescent tubes was stil happily spewing photons. There were several coolers like this, and none of the other ones were working, but still had power as the electronic thermostat still worked. One of the HVAC fans was working also. This place was also abandoned for about 20 years at the time the video went up. I can't find it now, otherwise I'd link it here. I guess it got deleted by one of the platform's snaps. I found it in my bookmarks and I can confirm. That video doesn't exist anymore, the link is dead. Edited because YT erased half my comment for some reason.
The upper pair of resistors are needed during start up. this biases the output high so that the lower transistor can draw enough current to drive the 3 winding transformer.
That circuit boards look like it was made in the 80's. Nothing wrong with that, much more pleasant to work with than the modern SMD ones when fixing stuff. But definitely didn't expect to see that.
Very well explained! I know these don't have much application anymore, but I would love to see a side-by-side comparison to the "more expensive" style you mentioned, and perhaps compare both to the vintage "buzzy" ballasts with the starter.
The way you explained how the current flows and what happens in the circuit was very helpful. I'm only a novice hobbyist and content like this is gold! There were a couple of things that stood out (at my level of knowledge): what happens when the capacitor fills up and the presence of a low pass? filter there which I did not pick up on my own untill you said it. A very enjoyable video!
I used to design and hand paint my own single-sided PCB's in the '70's. Not beautiful but they worked fine. Now things are much easier, cheaper and nicer.
These electronic ballasts were good. When tubes stopped working on the old coil wound ballasts, I simply moved them over to these electronic ballasts and they tubes started working again. Increased their life by 10%. My current 22w led tubelight has been running since three years. The old tubes barely ran over 12 months.
Our workshops and offices have a mix of fluorescent tube and LED lighting, the stock room has plenty of spare tubes left and we keep replacing until UV/heat damage makes the fitting or diffuser too brittle to carry on before replacing with LEDs. They do the job and as you point out often last a long time which is worth a lot in high roofed/inaccessible work areas.
Interesting evolution of fluorescent lighting. I'm still impressed that magnetic ballasts managed to do away with the starter. When we built our house in the early 1980's I installed a bunch of 40W T12 fluorescent tubes with magnetic ballasts. In 2013 I replaced them with 32W T8 tubes with electronic ballasts. Then last year I replaced them again with 14W & 17W T8 LED tubes and removed the ballasts as the tubes have built-in electronics. So far I'm happy with the LED replacement brighter and lower wattage. On this side of the pond it is becoming pretty common for commercial buildings to use PoE to implement smart lighting.
In the last 5 or so years, I've retrofitted most of the 4' fluorescent fixtures in my garage and shop with LED replacement tubes. The former occupants were 32-watt T8 lamps with electronic starters. I'd get about 5-6 years of service out of a lamp before the brightness declined seriously. The jury is still out on the LED replacements, but so far, so good. I've got plenty of spares, so if the LEDs start declining in brightness seriously, I'm prepared.
Shame to see that fluorescent are going away too. I always liked them. Much more reliable than most of the LED fittings available now. Some shops have half of their lights flickering because they're such poor quality. I'm not saying a fluorescent never had this problem. But at least you could replace the tube, or even the starter if it was of the older variety.
This is partly true - but i got the impression, the led designs are getting more reliable, at least the ones sold in stores like, Aldi, Lidl, Action. Not so sure with ebay. They're still overdriven and may degrade fast with light emission, that's hard to judge, especially in comparison to the also degrading fluorosent light output. But with current prices for electricity, at least here in Germany, i simply don't want to light shop or home with a bunch of fluorescents eating up 65 watt each any more, when i can achieve a sufficient somewhat comparable lighting for around 20 watt for the same area. Electricity bill adds up so quickly day after day these days, if it isn't just the living room lamp you pay for. So i throw the glassware out voluntarely to do my wallet a favor. Next story are replacement costs and overall costs over livespan if i wish to have the workdpace lightened instead of cosy. A fluorescent tube was never really cheap - so most of us used the tube, until it was hardly lighting at all - but the dim sucker still was consuming the same current like it was bright - for years, maybe decades to come. That wasn't exactly funny either. And these days fluorescent tubes are even more expensive, tendency still raising, whilst the retrofit led replacement at aldi or lidl costs a fraction of the flourescent for the same lamp trending downward. And it get's even cheaper per lumen per square meter workspace, when i switch to E27 fixtures, as long as i buy daylight versions of these bulbs.
@@kitecattestecke2303 Thanks. I'll check that offer. My current workshop has to be lit all day half a year and the other half year half a day half the lights on sunny days. But that's quite common. That's, why lighting costs are adding up - doesn't matter as long as the customer pays for expenses, but now it's just hobby and eats my own money.
I know they are not quite the same but the oldest of my LED lights here are passing on 13 years old by now and are still working fine despite pretty much 24/7 operation (a high/low LED bulb from Aldi way back in the day). I have only had to replace one of the LED lights which was around 8 years old at the time because the light output was way too low for the room.
Also a LOT of cookie cutter development homes built (in the midwest US at least) before LEDs were popular use the dual 4 foot fluorescent lamps in the kitchen (I think known as the cloud puff design?). Since it's easy to pop in a tube every few years, they probably hardly get replaced unless there's a renovation. Not looking to reno, I just replaced mine on its own with the LED version.
Cool explanation, going down the rabbit hole of ballast's past, the magnetic ones are really really amazing. Quite a dedication to the advancement of these lamps. There had been a suggestion to have a separate high frequency generator in office buildings to power these lamps that would operate with increased lumen per watt
Can you imagine the amount of radio frequency interference an HF generator would cause, with the wiring and fixtures creating a giant distributed antenna system?! Any alternative impedance matched coaxial wiring system would make it financially unviable.
To reiterate previous comments: Great explanation! It is truly amazing how this design has evolved to become so cost effective. Probably exemplary of so much we've come to take for granted these days.
Good morning Big Clive. I just thought I would remind you of a catchy tune to start your day out today! Bana Nà Mah ........... Do do ..da ..-do-do.. Mah Nà Mah Nà" Have a good day Big Clive!🙂👍
Fun side effect of the LED movement. On our production floor at work, we are all LED, but we use solar powered calculators. They are literally starving for energy. I've actually switched to doing a lot of my numbers by hand because by the time I track down one of our poor starving calculators I could have done it with pen and paper. Or I just do it in my head.
Many years ago, I pulled a temporary fluorescent fitting from a skip. It had been running from a 110V AC centre earthed supply (55V - earth - 55V) which is standard for building sites and temporary site lighting in the UK. On opening, I was surprised to find it used an autotransformer (to step the voltage up) in the same form factor as the magnetic ballast!
In the past, various trades used to make complete deathtrap contraptions from those for powering their 240V site radios from 110V. Usually just some wires and lots of insulation tape.
I still have a swing-arm type florescent lamp by my bed to read by, and the two 16" tubes in it have been going now for several years. I purchased two more tubes/bulbs, not long back, and stored them away, and I might buy a ballast, as well, because the lamp, to me, is much better than LED.
For me it's easier to understand the circuit if I think of the tap on the series filter capacitors as ground and the output is +170 and -170 volts. One end of the tube is connected to my ground and the other end swaps between +170 and -170. The 4.7 nf capacitor does double duty as a filament warmer and a series limiting impedance.
"What's that line from between the two 10uF capacitors doing (connects directly to the tube)?" A change in perspective makes that line the "0V" reference, and the far sides of those capacitors +170V and -170V. The two transistors form a push-pull output driving the inductors to the tube. The RC circuit driving the diac for start-up, and the diode preventing the diac from firing makes sense to me. I'm not so certain of the 2 R's and 1nF cap....
That was great. Thanks Clive for another fantastic video! The circuit reminds me of the little oscillator in the ozone generator that you reverse engineered a little while ago; especially the diac-based start circuitry. A few years ago the LED replacement "bulbs" for T40 fluorescent bulbs started appearing in my local Costco and I was tempted to refit my basement fluorescent fixtures to LEDs. BUT then I realized that my lights were dead reliable and I haven't swapped a tube in over 5 years. The LEDs seems to be all over-driven as you have mentioned in other videos and we aren't getting the lifetime/reliability that we should be getting from those devices. The LED bulb replacements were nearly $40 as I recall and I decided there was no benefit in retrofitting my basement.
I prefer a 6 foot rube and the old bimetallic starters and a big choke, which I still have in the garage. It just brings back memories of the good old days as i stand there in the dark after switching the lights on, listening to the genital tick tick of the starter. Plus the little pink flash of light from the end of the plastic starter can. You just don’t get this with LED’s where is the fun of not knowing when it light. 🙂
Interesting! When I moved to the EU some years ago I brought with me a few of the 4 foot twin tube fixtures. I also had purchased a bunch of GE solid state multi volt ballasts. As I installed these fixtures into utility rooms I replaced the 120 volt ballasts with the multi volt units. Work fine! As for tubes I lucked out buying 2cases of tubes from a liquidator who was selling out a store that had closed. $10 each case. After 16 years have only started to use tubes from second case. I also picked up on a used surplus military comms container that is equipped with 4 foot fixtures. 86 vintage so they are all T12 tubes with magnetic ballasts as well as a filter choke on the AC input. This type of container is used for military comms so any electrical noise must be kept to a minimum. Thought about a retrofit with led tubes but they are way too noisy for HF communications ( yes I am an amature radio operator ) . Does anyone know of a source for 4 foot LED tubes that run on either 12 or 24 volts DC?
I feel with you, used listening to shortwave radio throughout 70s and 80s. No fun anymore. I would use 12v 50 cm led strips, they come clear or milky in daylight color or yellowish with little clamps for mounting. I was pleased with the white ones for workspace lighting. There's no pulse involved as far as i can remember. But didn't try with SW.
I like how the pcb is laid out like the schematic is. I guess eliminating balancing resistors in the input electros has two reasons. 1 as mentioned is cost cutting. Another is that any dc bias on a flouro tube affects lifetime so removing the resistors essentially makes the caps block dc of the driving waveform.
The kitchen and the bathrooms here have ceiling fixtures for lots of 40-watt tubes, each on a one-tube heavy 1970s-era ballast. I’ve replaced every tube with a plug-in replacement LED array “tube” that runs fine off the old ballasts, not all of which drove the real tubes properly (several killed their tubes young). All the tubes went to the hazardous waste place at the county dump; I don’t know if they were disposed of properly but I don’t have a 40-watt tube here either now.
I think your right the circuit appears to be a blocking oscillator, relying on the base drive transformer to set the frequency. The parallel resitors and cap might be there in case the tube or wiring goes open to stop it from oscillating at RF frequencies.
Will work with the 3foot lamp, as that is basically a constant current driver, so will simply run the tube at roughly the right current, just like it does with the 4 foot tube.
Clive I use fluorescent tubes. 40W in the kitchen is over 10 years old. Replacement tube is 5€. Genuine Philips 10W LED light in sitting room on ES holder lasted 1 year cost 8€.
my workshop light is a dual T8 58W neutral white flourescent tube setup, upgraded from conventional ballasts to Osram "quicktronic professional" electronic ones probably 15 years ago and wired such that I can just turn on one of the two tubes. The tubes were used when i upgraded the ballasts and have lasted till 2017 when they both stopped firing in short succession (a week?) to each other. I replaced both with new 58W tubes... for a whopping 3eur a piece. Meanwhile I've had to replace countless more expensive LED lamps (GU10, E14, E27) after as little as 4 months due to various failure modes (usually catastrophic, visibly burnt chips etc). My oldest, non-modified LED lamps that are still working fine are just about approaching *half* of what the original used flourescent tubes managed, and ironically those LED lamps were cheapo ones (3W ISY from mediamarkt)
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same here. 20 years with fast electronic starter and it’s still going
Good video. An idea for a follow-up video would be to get some 40W tubes and make your measurements. Borrow tubes if possible. A detailed explanation of ballast theory and operation would be nice. I'm a little hazy on that and I can't be the only one. It may be true that fluorescent tubes do not find many applications in new installations, but there are countless old installations across the globe. These are usually production facilities and institutional settings of various sorts. When the lights go out, it's a problem to be immediately addressed so that the facility can proceed uninterrupted with normal operations. Maintenance staff will be dispatched to replace the tubes. When that doesn't work, an electrician will be called who will likely replace the ballast. With the lights back on, the problem is solved and no on one gives it another thought. Replacing and upgrading the lighting comes out of capital budgets and is often part of larger renovation projects. LEDs, if chosen appropriately, can reduce maintenance and energy costs significantly, but they're not cheap. It's an investment. Until that investment in time and money is made, there will remain a need and a market for fluorescent tubes and ballasts.
(shifty eyes) for yer tomatoes eh? Oh wait, they legalized it in half of the country now, shame homegrown is still illegal unless you have a permit in most places, overgrow the world!
That center tap is producing a virtual ground. The schematic is easier to understand if you write in 0 v at the center tap, then you've got a plus and minus 170V rail coming out of the bridge rectifier. The end of the tube connected to the midpoint is getting ±170V going to the ground at the other end. I think you may have the door on the wrong end of the feedback xfmr primary, but xfmr dots make my head hurt.
I think the dots are fine. When current flows into the dot on the primary the secondary current has to flow out of the dot to balance it. Or if you prefer to think of voltage, when a positive voltage is applied to the dot on the primary then all the other dots will go positive.
When I did the refit in my shop to remove ballast and install Led tubes, I carefully looked for ones with good reviews and hopefully aluminum backing for heat sinking. I installed my Hypericon tubes 6 years ago and the only failure was because one of the tombstones broke. Other than that they have been great.
Note the frequency is always highest, when the oscillator is unloaded, which will cause the impedance of that 4.7nF capacitor to be very low. The frequency drops, once the tube has struck, causing the impedance of the capacitor to increase, so it draws negligible current. It's the inductor in series with the tube limits the current through the tube, rather than the feedback winding. It will have a higher impedance, to the higher frequency, before the tube starts, so perhaps it's selected to form a resonant circuit with the 4.7nF capacitor, which will increase the current and voltage during start up.
When you said initially that you couldn't see any obvious current limiting, I immediately pointed at the feedback transformer, think "I bet that's it" though without any tangible proof. Your analysis confirmed that you thought exactly the same, but this time with evidence.
In my workplace we have backlights for movie posters... actually the frames have been designed by my boss and welded together by is brother. Essentially the frame is 1m high and 0,6ish wide, and the poster is taped at the corners to a 1 x 0,7m piece of 3mm semi-opaque plastic sheet that is forced between the frame sides. There are two 18W fluorescent tube fixtures in each frame. We have been using LED replica tubes in them with great success. Years ago the LEDs were rather expensive and everyone was already trying to get rid of the fluorescent tube stock. A "general store" of small hardware, household goods, decorative items, and a plethora of utter rubbish, which I very much liked (the store, but the rubbish too) was changing owners and they had huge discounts on some stuff. I saw a shitload of 30W fluorescent tubes sitting in a corner, sold for 0,20€ a piece, and it got me thinking... they were of optimal size to illuminate one poster frame with one tube, without making a brighter spot in the middle of the poster. BUT! And this is a big but! I tried to find prices for fixtures that took 30W tubes, and found out that the store had none, and in general, that size was virtually unobtainable or cost an arm, leg, and some other appendages.
Years ago, there was a term used for any start-up circuit for these and inverters, which was called a "tickler circuit." The switching transistors were tickled into operation.
My employer appears to have a policy (or the contractors that do the work) to replace fluorescent fittings with LED equivalent fittings on failure only. Unless in customer and public areas, where they fit the dim/bright sensor LED fittings. These change to full brightness when they detect movement, then after a while go back to their dim mode. Occasionally (such as in stairways) they use LED fittings that also have movement sensors (radar type, as they can detect through walls) that switch the LEDs off completely if no movement has been detected for a while.
I used to do maintenance for bp oil's head office in Canary wharf. It was mostly fluorescent fittings with with "digital" ballasts(with Dali dimming function). The ballast circuitry was a lot more complex, With a ton of suppression and filter circuitry. The failed ballasts provided me with a constant stream of components to salvage from them. Class XY capacitors for example. My colleagues thought I was crazy for stripping down old florescent ballasts😂😂🤔.
In my experience, LED lamps fail due to the 400 volt filter capacitor going open. If you don't abuse them, LEDs will last a long time. though maybe not as long as a good quality flourescent fitting with a conventional ballast. Replacing the tube is easy and cheap. With electronic ballasts the tube usually outlives the ballast. I think modern LED lights are getting more energy efficient than their counterparts, so I'm not getting any more CFLs. When they go they are replaced with LED equivalents. I always like your content, Clive, and although I'm an old hand I still sometimes learn something from you. Keep it up!
Almost identical to the circuit used for the old 12 Volt halogen lamp electronic transformers. Think of it as a half bridge and if you scope the output you will see trains of high frequency triggered by the diac at a much lower frequency. Not sure if it was intentional or happened by chance, but, due to the action of the toroidal feedback transformer, you need to give it a load before it starts to work. After that, it only supplies as much power as you pull from it, hence the misquoted power factor figures always given with these devices. Big problem is that as the tube ages, it pulls more current and the switching transistors tend to go off with a bang.
My flat in London has TWO fluorescent lights - a little square one in the bathroom and a “normal” 4 footer in the kitchen. Kitchen recently (2 weeks) needed a new starter…
Thanks for reminding me I need to do something with a light fixture with a dying ballast in it. *OMP* Okay 90 minutes later and I've found appropriate LED replacement tubes with the needed parts included for the retrofit. Only $21 for each kit so for less than $10 more than a new ballast and tubes I can retrofit both fixtures.
Old ballast for fluorescent tubes lasted decades. On the other side, I have a bunch of these electrochinese things that have failed. Have replaced them with LED tubes (that fails fast too). The few of these electronic ballasts that still works burns (literally cooks) tubes in less than a year. Screw all of that "sustainable" crap. I've scored a lot of vintage industrial fluorescent fixtures (the long tube flavor) in a dumpster, and I will put them in good use replacing the modern ones... (also old starters makes the random flickering lightshow when turned on, especially satisfying when there are many turned on at once)
I think the two 680 k and 1 nF help with the diode's reverse recovery time. I also think the electrodes will stay hot long enough for the plasma to drain the filter caps to a moderately safe level... the oscillator is still powered after all.
I have changed all my lights to LED 4 years ago. I bought an assortment of new incandescent lightbulbs and put in storage in case I needed some for a heating need.
Half bridge auto generator (electronic transformer) the 1n cap and resistors are to probably fine tune the frequency or add a little dead time. 👍great video as always Clive Steve
The vans used by (the UK) post office trains use to use 24V DC electronic ballasts to drive the fluorescent fittings on these trains. The reason being that the vans used a 24V DC electric system. I don’t however know what size/type the tubes were (they were all smashed up on the van that I saw, thanks to the vandals).
Best circuit. I wonder if that pink capacitor couples some mains-derived voltage ripple to the base circuits to help sync the oscillator frequency to a multiple of mains frequency.
Not saying they were identical to these, but these cheap Chinese ballasts caused so many fires in Afghanistan. When I got to Herat, I had to implement some basic electrical safety standards and specified all ballasts must meet CE standards at a minimum... So they found some of these dodgy ones with CE labels of varying authenticity (which isn't uncommon as I've seen even name brand devices with improperly formatted CE logos). Our better contractors at least got Turkish made ballasts.
I have a CFL box for curing resin (nails and other stuff), and when I got it, I checked if it works and then disassembled to see what's inside. It happened many months ago, but as far as I can recall, it has a tiny microcontroller (for timed mode), and an oscillator circuit, some capacitors and a three-winding (IIRC) inductor on a ferrite bead. I had no idea what was the circuit, but now it feels like it was something similar to what you showed here.
Nice explanation. Looks like if you installed a jumper at Bx it would allow operation from 120VAC - voltage doubler- (or blow it to h-e-double-hockey-sticks on 240)..
I use Fluorescent Lamps (a two tube fixture) in my garage. I just changed out the factory ballast last year -- the original was installed in 2004. I actually kind of wish I had another one, tbh.
Have a tridonic ballast which has failed, both transistors(3DD4244D) blown, carbonising around mains input fuses, neutral fuse open circuit. Do you think i would be able to just replace transistors or maybe another component has caused this?
Being less than young, I remember the horrors of the nasty tar filled transformers in the original fluorescent fixtures that often ended their life with a burn and smoke. The testing company I worked for was in the basement of an old bank building with questionable air movement, having one of these things go off was a Chernobyl quality event. A smell that you can taste... ah the memories.
I still have a fluorescent t8 lamp in my bedroom, no fixture, just a 120v ballast with a single wire going to each end of the tube, it drives it like a ccfl without touching the filaments so it has been in operation atleast 10 hours a day for the last 10? Years, the only non compact florescent left in the house i think? As bulbs have been burning out I've just replaced the fixtures with Edison screws so i can pop LED bulbs in as they are needed or even incandescent if I'm feeling naughty or need an additional heat source for specialized purposes
In addition from another comment thread, My favorite has discharge lamps all use metal salts and a very hot arc, 1000 watts of limited band orange light is so lovely, reminds me of sweet home Chicago, you can always find your bearings just by looking up at the clouds and finding the orange glow, sadly the glow isn't as orange anymore because of the trend for LEDs replacing them, i still want a low pressure sodium lamp.... Never got my hands on 1
In the lift industry LED is taking over but I’m not sure if cheap ones are being supplied but the LED kits are learning about 6 months rather than the amount of years the old fluorescent ones did
I had a couple of this style of ballast for my fluro lamps before I went LED. They worked but were rough on the lamps, no preheat, just blast breakdown voltage at them. Would have been stripping the emitters for sure. There is one thing i do remember about them though. If the lamp was cold, say 10c or less, you could see the lamps were being run at 10kHz or so by the size of the dim bands running along them compared to how they looked when cold with 50/100Hz.
As some one that spent a large part of my working life dealing with fluorescent light fixtures they were great till the government implemented energy saving legislation. Manufactures had to introduce the ALTO bulb they were hit or miss right out of the box. It got to the point working on a 2 bulb fixture you took 4 bulbs and a new ballast with you on all the work orders. I rip the ballast out swap in retro fit leds now to keep my sanity!
I wonder if the DIAC startup circuit is why it doesn't need the series capacitor? At startup, both transistors will be off, and no current will flow through the tube. The other style use the noise in the transistors to start the oscillation, and the capacitor might need to be there so it can amplify enough to get it oscillating reliably. That, or it's in that linear region for a relatively long time and the capacitor stops large currents from flowing. In the US, the ballast I took apart works very similar to this; it reminds me of the old AT power supplies using two capacitors, a bridge, and the switch for 120/240 that modifies the diode bridge connection so it either straight rectifies (240V) or makes it into a doubler (120V) and thus the supply runs on the same voltage internally in both cases.
We have both led and florescent lights at my work place. After 20 years I am finally having to replace ballasts. The led lights are more recent and so far only one has failed.
Thank you very much for this, I couldn't understand how the feedback transformer works when I tried to fix a broken lamp. (There are a UV lamps out there that still use those). That power supply was on the kind of a a circular custom-shaped board that would fit into the base of the lamp. It had a similar design with a couple more transistors and diodes here and there.
The electronic ones I've opened were filled with potted black stuff, covering all the components. I've slowly replaced the ones in my garage with direct wire no ballast needed L.E.D tubes.
I am retired now but I was asked to increase lighting in a liitle used room, I was going to fit LED light and I was checking wholesale prices and I found I could buy a twin 4 foot fluorescent fitting including tubes and VAT for just over £5:00. Figured the payback on LED was abot 10-15 years so went fluorescent
I had an actual 4ft fluorescent tube in the basement go dimmer... and dimmer... and dimmer... 'til it barely glowed. Replaced it with a new bulb, which was nice and bright... for about a week, then went dim again. Got a plug'n'play LED stick (ie, no need to remove the ballast and/or rewire the fixture), and it's chugging along nicely for about a year. Nice 4000K, and not eye-scorching 7000K anymore. Did the same for 3ft tubes in the kitchen above the windows.
I have fluorescent lights in my garage - one failed recently and I'd been considering changing to LED strips, but then someone on Freecycle was giving away a dozen fluorescent lamps exactly right for my garage! So that's me sorted for the next fifty years...
This reminds me of an electronic ballast I found in an unusually cheap and lightweight residential high-pressure-sodium yard light several years back when I was collecting HID lighting fixtures. Unlike most of these luminaires that used conventional iron ballasts, this one had a single rectangular board inside with all the componentry built on, including the photosensor for dusk-to-dawn operation. Mostly discrete components with maybe an IC or two. Makes me curious how similar it is to the fluorescent lamp ballast circuitry.
The 50 watt hPS Lights Of America Model 9051 "WallPack" ? I have the 42 watt CFL version (Model 9042) that I converted to house an 18 watt Low Pressure Sodium (SOX) lamp. The schematic for both the fluorescent and the HPS versions are published on Sam's Repairfaq
@@yuandrew Yes, I think that's the one! I didn't know they had schematics on Sam's site. That's pretty cool. We may have had the fluorescent version too. Problem is, it seems like most of LOA's products always had QC issues. Both the fluorescent and HPS units died shortly after we got them. Our replacement HPS unit finally managed to outlive its lamp, and was still working the last time I plugged it in.
Nice a ballast video ! I really like fluorescent lights and love them when they start to flash before dying. But sounds dangerous this ballast and cheap
Was trying to diagnose somebody's ring light. It happens to be a ceiling fan that uses a fluorescent tube in a ring, I've only ever seen this once. They bought an LED retrofit which slightly doesn't fit the tabs that hold the bulb in. And in an attempt to figure out why it wasn't working I bypassed the ballast and blew the internal fuse. Apparently they never intended the unit to be direct wired. annoying because the ballast in the ceiling fan was bad after diagnosing with a known good glass bulb. And no not necessarily standard as in no standard light sockets it had a prepare pin snap in design. And ceiling fans are notorious for not having any extra space.
i could be crazy, but it doesn't look like that green deal between the two smoothing capacitors connects to their output, the orange circuit. if you ask me it pretty clearly goes from the red circuit to the pink circuit.
is this what you mean with not being up at sociable hours? There's a certain type of electrical engineer and/or technician that would love to work 9 to 5, but pm to am. I wonder what that's about...
I have some really old fluorescent fixtures that have the super old ballast's in them. The big heavy ones. For some reason I've never been able to wrap my head around how a ballast works. I know why you need them. But I don't really know how they limit current.
A resistor can be used to limit current and that's what _ultra_ cheap fluorescent fixtures use. Regular series-connected magnetic ballasts are just inductors. Inductors have an impedance to AC so they basically emulate a resistor without wasting all the power. More advanced "rapid-start" ballasts were standard for longer tubes in the US and they are basically step-up transformers with leakage inductance.
They're less and less but some places still have fluorescents. We did until they stopped selling fluorescent tubes and came out with the universal drop-in ones that don't require rewiring... Although even then I waited until the tubes were getting dim and needed to be replaced anyway. I'd love to know how the drop-in replacement ones work that are compatible with T11, T8, and direct wire without any modifications. Unfortunately I learned they are real glass when one broke so it would be a major mess to tear one down and reverse-engineer.
I'd use that ballast! 40 watt 4 foot tubes are super bright now, and have a nice color rendition compared to the old days. I have a "vintage" dual tube 4 foot fixture in my walk in closet but it's still using the old purely inductive ballast which gives that nice growl sound.
The hum was sometimes nice and sometimes way too loud, i recall moments from school where we loudly hummed when teacher was talking and then blamed it on the lights.
@@plainedgedsaw1694 If the ballast in my closet gets that loud it's going on the curb on trash day. In the 9th grade the public school had big incandescent bulbs. I couldn't believe it. They didn't flicker or hum though. On warm days we turned them off and relied on natural light to keep the room cooler.
Isn't the 1n cap just there for pre-heating the filaments? I can't see any other current path till the diac breaks over causing the lower npn to switch.
Clive: I know we are behind the times here in the USA, but hospitals use a ton of fluorescent lamps mostly in offices, hallways and stairwells, especially if the area hasn't been remodeled or updated in many years. Most fixtures use compact fluorecscents and rarely LED, but that is slowly changing to LED "strip" lamps and some four foot drop in retrofit LED lamps that don't require the ballast being removed, as a side note about 20 years ago a hospital I worked in did a "retrofit" of the fluorescent fixtures from a T-12 lamp to T-8 lamp and removing the old magnetic ballasts (many of them were of the potted type some with PCB's.) to an electronic ballast. The new electronic ballast were capable of dual input voltages (120 or 277 volt). Imagine how many fixtures could be run on one 277 volt, 20 amp circuit! Oh, and the operating theatres were notorious for six lamp-four foot fluorescent lamps, Because the operating rooms almost never were remodeled unless being changed to a different configuration for new equipment or procedures, the operating rooms are large source of revenue for a hospital and to shut a room down and do the infection control/dust mitigation was kind of big money. -John
Wiring a newly built hospital in the us four years ago and general contractor chose the cheaper option for lighting. All fluorescent fixtures in a brand new hospital just blew my mind
I was electrical maintenance in the '90s at a hospital...we were slowly replacing the older magnetic ballasts with electronic ones ( as magnetic ones failed, they were replaced with newer electronic ones) The old magnetic ones would have " earwax" running out of them sometimes when they failed.
We didn't shut the power off when replacing ballasts! Really couldn't. I always installed a AG-3 fuse and holder in line to make it easier for the next guy...
You're right...they didn't want to shut down the OR for anything. I had to replace a 24volt, 35 amp transformer that powered the surgical lights...took a few hours ( difficult location), I got chewed out because some estimate said it only took 45 minutes...I believe this hospital had around 3000 florescent fixtures ..
Same here in Brazil. We still have some surgery lights that use incandescent bulbs, as an example of how they sometimes prefer to not updated to new tech if it's working.
@@Bleats_Sinodai a lot of dentists still use incandescent/halogen lights because they have the reflectors that reflect most visible light, but pass infrared so heat goes the opposite direction of the light output (much like some 50W MR/GU halogen lights).
There are a lot of fluorescent lights in many old buildings all over Europe too. My office even has a fluorescent light that is so old the tubes for it aren't sold anymore.
Thanks for the video.
Not that long ago, flourescent tubes were used for lighting in pretty much every school and office building in my part of the world. Nowadays, they have mostly switched to LED panels.
What I hate about modern LED lamps is that they are often deliberately built not to last long (especially the cheaper ones). Manufacturers tend to overdrive the LEDs a lot to squeeze more light out of a smaller number of diodes causing them to die early. And often the death of a single LED package kills the entire light because they are wired in series.
Florescent lamps are still popular in Sudan.
I'm going to continue to use fluorescent lighting in my home and have stocked up on fluorescent tubes and other spares. As a toddler in the 70s they fascinated me, the way a tube could light so brightly and evenly. Was always also fascinated by the different start up behaviours. In 1978, only a few weeks after starting school, long thin boxes with purple text were delivered to the school which contained 8ft Thorn pop packs. These were to replace tungsten lighting. Still remember as the winter months took hold how well these lights lit the room, they had what was at the time cutting edge lighting technology in the form of 100w Krypton tubes.
Just don't get/stay too close to them, I used to use em as a UV source for curing UV solder mask, etc.
The sun was also good, but well, this being Ireland, its rarer than dinosaur farts 😀
Now I use a dedicated UV source, but you get the idea.
"Quite irrelevant, because . . . . Who uses fluorescent tubes these days?"
Well, some months ago, I was reverse-engineering a four-little-fluorescent-tubes bulb circuit (more complex but also more compact than this in the video) and one part of the push-pull circuit made no sense to me, it seemed to be reversely fed. Your explanations have been very relevant for me to understand how it worked! Thanks a lot!
Was it in a nail polish curing unit? They use the same circuit, but four inductors, one per tube.
@@bigclivedotcom No, it was just a light bulb. I've just retrieved it from a drawer and realised it's just two, not four, but U-shaped, tubes, inter-communicated via a short (4 mm.-long) transversal tube. Branded IKEA, model no. 2P211. Specs: 220-240V, 96 mA, 50-60Hz, 11W, 600 lumen. Made in China.
A light lamp, not bulb, of course.
Here in the US, electronic ballasts are pretty simple things--many times even simpler than the unit described. Very often, the tube heaters are not used at all--both sides of the tube heater are tied together and only a single wire goes to each end of the tube. I've got a pile of old General Electric Industrial 32/40 watt 120V ballasts that date back to the late 80s and they work just this way. The nice thing about electronic ballasts is that they're very light when compared to the old iron-core ones--a benefit when you're retrofitting ceiling-mounted fixtures.
I still run fluorescent because I like it! On magnetic chokes too. The extra warmth helps heat the house most of the year anyway.
That ballast doesn’t have any tube end-of-life shutdown, so be prepared for cracked glass and melting lampholders if a tube fails and the ballast keeps driving it!
Never seen this happen, i only seen them failing to start.
the full wave rectifier is actually constructed with series capacitors to allow easy conversion to 115V input, just populate the "BX" position with a jumper and it will become a doubler-rectifier. That's also the reason for the center tap going to the lamp.
That was my first guess as well but stupidly that's not the case. From what I can see on the board photos both ends of "BX" are actually connected together.
@@eDoc2020 Yeah, but its a very easy and reasonably safe trace to cut to separate them. (I thought that position might be for a ferrite bead, so I paused the video there and spent a second staring at it. It looked like it was designed to be cut, but I couldn't figure out why you'd want to do that. This is a much better explanation for that footprint. I feel slightly dumb for not recognizing what you guys did.)
(To preface, I posted this comment on the day you made this video public, and it somehow ended up in the comment section of some random RUclips short (found out when I got a very confused sounding reply from someone), so I guess RUclips is broken, this out of the way)-Very cool to see how these electronic ballasts work. Also ironic that you uploaded this because I actually just converted one of my fluorescent fixtures from electronic to magnetic preheat ballast haha. Electronic ones are good and all, but they are really rough on the tubes, the old preheat ballasting systems were much more gentler when it comes to starting up the lamp, pretty important with my fixture since all my tubes are vintage, in fact I have a Sylvania tube that dates back to 1952! (this one actually happens to be an F8T5 type tube that I found in a vintage manual preheat desk lamp, which explains why the tube is still old and still works!) I’ve also always liked the Blinky startups 😉
I've noticed some oddities in the comments for a while. Usually referring to a completely different video.
fluorescent lights and gas discharge tube devices in general are incredible. sort of sad, but also understandable seeing them slowly being phased out. it’s a bit silly. theoretically a perfect fluorescent light could last more than the lifetime of a human being and much longer in ideal conditions. but of course we live in the real world, so achieving a perfect light or perfect conditions is impossible, but still, they we’re able to last long without it just being a stroke of luck. with proper setup they were reliable and durable. but then came CFLs. oh boy. we wanted the luxury of using our good ol’ edison sockets and having all the benefits of the reliability and durability of big fluorescent tubes. turns out sticking a high voltage ballast into the space of a golf ball with extremely limited airflow isn’t as easy as it sounds (well it doesn’t even sound easy, but you know what i mean). so they broke. the more they broke the more people expected them to break, and the more people expected them to break the more manufacturers turned to making cheap, but replaceable bulbs rather than making then a bit expensive, but long lasting. all of this sounds waaay too familiar. LEDs anyone?
i didn’t expect to write an essay, but here we are lol. don’t get me wrong, i love leds, but i think we have become way too lenient when it comes to things breaking. and the more lenient we become, the more things will inevitably break
Well said.
My favorite has discharge lamps all use metal salts and a very hot arc, 1000 watts of limited band orange light is so lovely, reminds me of sweet home Chicago, you can always find your bearings just by looking up at the clouds and finding the orange glow, sadly the glow isn't as orange anymore because of the trend for LEDs replacing them, i still want a low pressure sodium lamp.... Never got my hands on 1
@@frogz I'm young enough to only recall seeing low pressure sodiums in my early childhood, but i kinda miss them everytime i see picture of them lighting up a street in pure yellow cancelling all other colors.
We shouldn't feel bad about writing more online. Your comment is maybe one page in a novel. Social media has made people lazy. We're having interesting discussions here. The fact that it fills up a small smart phone screen or a comment box on a computer deceives the mind, it really isn't very much to read at all.
@@liam3284 rapid start aka high voltage Spike instead of heating elements that can burn out
I have seen abandoned buildings still powered here on RUclips. Many of those are the old magnetic ballasts, and they sem to last forever. There was one place that was decayed so much that things were falling out of the ceiling. Most of the hallway lighting was still working 20 years after the place closed to the public for the final time. This place was built in the thirties if I remember right.
The newer electronic ones (mostly) seem pretty good too. There was another video I saw of a small abandoned strip mall that was still powered. A small general store (Think Dollar General, but it wasn't that.) had power still and a few lights were still on, but flickering. There was a TRUE reach in display fridge that was still working fully, Keeping temperature, sounded good and one of the fluorescent tubes was stil happily spewing photons. There were several coolers like this, and none of the other ones were working, but still had power as the electronic thermostat still worked. One of the HVAC fans was working also. This place was also abandoned for about 20 years at the time the video went up. I can't find it now, otherwise I'd link it here. I guess it got deleted by one of the platform's snaps.
I found it in my bookmarks and I can confirm. That video doesn't exist anymore, the link is dead.
Edited because YT erased half my comment for some reason.
I wonder if people realise that a building like that will use a lot of ambient power when they turn the main switch on.
The upper pair of resistors are needed during start up. this biases the output high so that the lower transistor can draw enough current to drive the 3 winding transformer.
That circuit boards look like it was made in the 80's. Nothing wrong with that, much more pleasant to work with than the modern SMD ones when fixing stuff. But definitely didn't expect to see that.
Very well explained!
I know these don't have much application anymore, but I would love to see a side-by-side comparison to the "more expensive" style you mentioned, and perhaps compare both to the vintage "buzzy" ballasts with the starter.
The way you explained how the current flows and what happens in the circuit was very helpful. I'm only a novice hobbyist and content like this is gold! There were a couple of things that stood out (at my level of knowledge): what happens when the capacitor fills up and the presence of a low pass? filter there which I did not pick up on my own untill you said it. A very enjoyable video!
Single sided through hole easy to trace board. This really is a blast from the past :-)
Ballast from the past
The visual symmetry makes it nice to at and easier to screen after production for component stuffing errors, if that were still a thing.
I used to design and hand paint my own single-sided PCB's in the '70's. Not beautiful but they worked fine. Now things are much easier, cheaper and nicer.
Starts a video complaining about the government, this is why I'm subbed. Love the content
These electronic ballasts were good. When tubes stopped working on the old coil wound ballasts, I simply moved them over to these electronic ballasts and they tubes started working again. Increased their life by 10%. My current 22w led tubelight has been running since three years. The old tubes barely ran over 12 months.
Our workshops and offices have a mix of fluorescent tube and LED lighting, the stock room has plenty of spare tubes left and we keep replacing until UV/heat damage makes the fitting or diffuser too brittle to carry on before replacing with LEDs. They do the job and as you point out often last a long time which is worth a lot in high roofed/inaccessible work areas.
The circuit is an (power) oscillator, which lifts the 50Hz to 30kHz, which reduces the ballast inductor from a iron block to a 5gramm ferrite.
Interesting evolution of fluorescent lighting. I'm still impressed that magnetic ballasts managed to do away with the starter. When we built our house in the early 1980's I installed a bunch of 40W T12 fluorescent tubes with magnetic ballasts. In 2013 I replaced them with 32W T8 tubes with electronic ballasts. Then last year I replaced them again with 14W & 17W T8 LED tubes and removed the ballasts as the tubes have built-in electronics. So far I'm happy with the LED replacement brighter and lower wattage.
On this side of the pond it is becoming pretty common for commercial buildings to use PoE to implement smart lighting.
In the last 5 or so years, I've retrofitted most of the 4' fluorescent fixtures in my garage and shop with LED replacement tubes. The former occupants were 32-watt T8 lamps with electronic starters. I'd get about 5-6 years of service out of a lamp before the brightness declined seriously. The jury is still out on the LED replacements, but so far, so good. I've got plenty of spares, so if the LEDs start declining in brightness seriously, I'm prepared.
The networked lighting is fine until a rogue node takes out an entire network or causes mass glitching.
Shame to see that fluorescent are going away too.
I always liked them. Much more reliable than most of the LED fittings available now.
Some shops have half of their lights flickering because they're such poor quality.
I'm not saying a fluorescent never had this problem. But at least you could replace the tube, or even the starter if it was of the older variety.
This is partly true - but i got the impression, the led designs are getting more reliable, at least the ones sold in stores like, Aldi, Lidl, Action. Not so sure with ebay. They're still overdriven and may degrade fast with light emission, that's hard to judge, especially in comparison to the also degrading fluorosent light output.
But with current prices for electricity, at least here in Germany, i simply don't want to light shop or home with a bunch of fluorescents eating up 65 watt each any more, when i can achieve a sufficient somewhat comparable lighting for around 20 watt for the same area.
Electricity bill adds up so quickly day after day these days, if it isn't just the living room lamp you pay for.
So i throw the glassware out voluntarely to do my wallet a favor.
Next story are replacement costs and overall costs over livespan if i wish to have the workdpace lightened instead of cosy. A fluorescent tube was never really cheap - so most of us used the tube, until it was hardly lighting at all - but the dim sucker still was consuming the same current like it was bright - for years, maybe decades to come.
That wasn't exactly funny either.
And these days fluorescent tubes are even more expensive, tendency still raising, whilst the retrofit led replacement at aldi or lidl costs a fraction of the flourescent for the same lamp trending downward.
And it get's even cheaper per lumen per square meter workspace, when i switch to E27 fixtures, as long as i buy daylight versions of these bulbs.
@@werner.x then go to Hornbach and check FL-tube price.. They are wattage reduced since some years and the light itself is
@@kitecattestecke2303 Thanks. I'll check that offer.
My current workshop has to be lit all day half a year and the other half year half a day half the lights on sunny days.
But that's quite common.
That's, why lighting costs are adding up - doesn't matter as long as the customer pays for expenses, but now it's just hobby and eats my own money.
I know they are not quite the same but the oldest of my LED lights here are passing on 13 years old by now and are still working fine despite pretty much 24/7 operation (a high/low LED bulb from Aldi way back in the day). I have only had to replace one of the LED lights which was around 8 years old at the time because the light output was way too low for the room.
Also a LOT of cookie cutter development homes built (in the midwest US at least) before LEDs were popular use the dual 4 foot fluorescent lamps in the kitchen (I think known as the cloud puff design?). Since it's easy to pop in a tube every few years, they probably hardly get replaced unless there's a renovation.
Not looking to reno, I just replaced mine on its own with the LED version.
Clive, thanks for the Saturday streams.
Cool explanation, going down the rabbit hole of ballast's past, the magnetic ones are really really amazing. Quite a dedication to the advancement of these lamps.
There had been a suggestion to have a separate high frequency generator in office buildings to power these lamps that would operate with increased lumen per watt
Can you imagine the amount of radio frequency interference an HF generator would cause, with the wiring and fixtures creating a giant distributed antenna system?! Any alternative impedance matched coaxial wiring system would make it financially unviable.
To reiterate previous comments: Great explanation! It is truly amazing how this design has evolved to become so cost effective. Probably exemplary of so much we've come to take for granted these days.
Good morning Big Clive.
I just thought I would remind you of a catchy tune to start your day out today!
Bana Nà Mah ...........
Do do ..da ..-do-do..
Mah Nà Mah Nà"
Have a good day Big Clive!🙂👍
Fun side effect of the LED movement. On our production floor at work, we are all LED, but we use solar powered calculators. They are literally starving for energy. I've actually switched to doing a lot of my numbers by hand because by the time I track down one of our poor starving calculators I could have done it with pen and paper. Or I just do it in my head.
Many years ago, I pulled a temporary fluorescent fitting from a skip. It had been running from a 110V AC centre earthed supply (55V - earth - 55V) which is standard for building sites and temporary site lighting in the UK.
On opening, I was surprised to find it used an autotransformer (to step the voltage up) in the same form factor as the magnetic ballast!
In the past, various trades used to make complete deathtrap contraptions from those for powering their 240V site radios from 110V. Usually just some wires and lots of insulation tape.
I still have a swing-arm type florescent lamp by my bed to read by, and the two 16" tubes in it have been going now for several years. I purchased two more tubes/bulbs, not long back, and stored them away, and I might buy a ballast, as well, because the lamp, to me, is much better than LED.
For me it's easier to understand the circuit if I think of the tap on the series filter capacitors as ground and the output is +170 and -170 volts. One end of the tube is connected to my ground and the other end swaps between +170 and -170. The 4.7 nf capacitor does double duty as a filament warmer and a series limiting impedance.
That's how I looked at it too. Either or though really. But yeah easier to visualize in my head
"What's that line from between the two 10uF capacitors doing (connects directly to the tube)?" A change in perspective makes that line the "0V" reference, and the far sides of those capacitors +170V and -170V. The two transistors form a push-pull output driving the inductors to the tube. The RC circuit driving the diac for start-up, and the diode preventing the diac from firing makes sense to me. I'm not so certain of the 2 R's and 1nF cap....
Elegant, efficient, design. Clever, without going too cheap.
_"That was sarcasm"_ , Oh no Clive, that was borderline passive aggressive snark. I approve!
That was great. Thanks Clive for another fantastic video! The circuit reminds me of the little oscillator in the ozone generator that you reverse engineered a little while ago; especially the diac-based start circuitry.
A few years ago the LED replacement "bulbs" for T40 fluorescent bulbs started appearing in my local Costco and I was tempted to refit my basement fluorescent fixtures to LEDs. BUT then I realized that my lights were dead reliable and I haven't swapped a tube in over 5 years. The LEDs seems to be all over-driven as you have mentioned in other videos and we aren't getting the lifetime/reliability that we should be getting from those devices. The LED bulb replacements were nearly $40 as I recall and I decided there was no benefit in retrofitting my basement.
I prefer a 6 foot rube and the old bimetallic starters and a big choke, which I still have in the garage.
It just brings back memories of the good old days as i stand there in the dark after switching the lights on, listening to the genital tick tick of the starter.
Plus the little pink flash of light from the end of the plastic starter can. You just don’t get this with LED’s where is the fun of not knowing when it light. 🙂
Much respect for my fav engineer BigC🙏 im learned many things from this channel and now I can easily analyse any circuit schematics ❤️
"Big C" makes him sound like a Cancer! 👎🤣
@Marc Se7en yeah bro i wrote it like that because i was afraid of making a mistake in the spelling :D
Makes a nice change from a capacitive dropper! Quite interesting electronics and love the symmetrical output driver.
Interesting! When I moved to the EU some years ago I brought with me a few of the 4 foot twin tube fixtures. I also had purchased a bunch of GE solid state multi volt ballasts. As I installed these fixtures into utility rooms I replaced the 120 volt ballasts with the multi volt units. Work fine! As for tubes I lucked out buying 2cases of tubes from a liquidator who was selling out a store that had closed. $10 each case. After 16 years have only started to use tubes from second case.
I also picked up on a used surplus military comms container that is equipped with 4 foot fixtures. 86 vintage so they are all T12 tubes with magnetic ballasts as well as a filter choke on the AC input. This type of container is used for military comms so any electrical noise must be kept to a minimum. Thought about a retrofit with led tubes but they are way too noisy for HF communications ( yes I am an amature radio operator ) . Does anyone know of a source for 4 foot LED tubes that run on either 12 or 24 volts DC?
I feel with you, used listening to shortwave radio throughout 70s and 80s.
No fun anymore.
I would use 12v 50 cm led strips, they come clear or milky in daylight color or yellowish with little clamps for mounting. I was pleased with the white ones for workspace lighting. There's no pulse involved as far as i can remember. But didn't try with SW.
I like how the pcb is laid out like the schematic is. I guess eliminating balancing resistors in the input electros has two reasons. 1 as mentioned is cost cutting. Another is that any dc bias on a flouro tube affects lifetime so removing the resistors essentially makes the caps block dc of the driving waveform.
The kitchen and the bathrooms here have ceiling fixtures for lots of 40-watt tubes, each on a one-tube heavy 1970s-era ballast. I’ve replaced every tube with a plug-in replacement LED array “tube” that runs fine off the old ballasts, not all of which drove the real tubes properly (several killed their tubes young). All the tubes went to the hazardous waste place at the county dump; I don’t know if they were disposed of properly but I don’t have a 40-watt tube here either now.
I think your right the circuit appears to be a blocking oscillator, relying on the base drive transformer to set the frequency. The parallel resitors and cap might be there in case the tube or wiring goes open to stop it from oscillating at RF frequencies.
Will work with the 3foot lamp, as that is basically a constant current driver, so will simply run the tube at roughly the right current, just like it does with the 4 foot tube.
Clive I use fluorescent tubes. 40W in the kitchen is over 10 years old. Replacement tube is 5€. Genuine Philips 10W LED light in sitting room on ES holder lasted 1 year cost 8€.
same here. 8 years and it’s still going strong
my workshop light is a dual T8 58W neutral white flourescent tube setup, upgraded from conventional ballasts to Osram "quicktronic professional" electronic ones probably 15 years ago and wired such that I can just turn on one of the two tubes. The tubes were used when i upgraded the ballasts and have lasted till 2017 when they both stopped firing in short succession (a week?) to each other. I replaced both with new 58W tubes... for a whopping 3eur a piece. Meanwhile I've had to replace countless more expensive LED lamps (GU10, E14, E27) after as little as 4 months due to various failure modes (usually catastrophic, visibly burnt chips etc). My oldest, non-modified LED lamps that are still working fine are just about approaching *half* of what the original used flourescent tubes managed, and ironically those LED lamps were cheapo ones (3W ISY from mediamarkt)
same here. 20 years with fast electronic starter and it’s still going
Good video. An idea for a follow-up video would be to get some 40W tubes and make your measurements. Borrow tubes if possible. A detailed explanation of ballast theory and operation would be nice. I'm a little hazy on that and I can't be the only one.
It may be true that fluorescent tubes do not find many applications in new installations, but there are countless old installations across the globe. These are usually production facilities and institutional settings of various sorts.
When the lights go out, it's a problem to be immediately addressed so that the facility can proceed uninterrupted with normal operations. Maintenance staff will be dispatched to replace the tubes. When that doesn't work, an electrician will be called who will likely replace the ballast. With the lights back on, the problem is solved and no on one gives it another thought.
Replacing and upgrading the lighting comes out of capital budgets and is often part of larger renovation projects. LEDs, if chosen appropriately, can reduce maintenance and energy costs significantly, but they're not cheap. It's an investment. Until that investment in time and money is made, there will remain a need and a market for fluorescent tubes and ballasts.
As a nerd obsessed with plasma I will never replace fluorescent or other discharge lamps with LED. It will never give the same feeling.
Fluorescent lights are making a comeback due to these awesome flowers they can grow.
They work good in the vegetative stages.
(shifty eyes) for yer tomatoes eh? Oh wait, they legalized it in half of the country now, shame homegrown is still illegal unless you have a permit in most places, overgrow the world!
That center tap is producing a virtual ground. The schematic is easier to understand if you write in 0 v at the center tap, then you've got a plus and minus 170V rail coming out of the bridge rectifier. The end of the tube connected to the midpoint is getting ±170V going to the ground at the other end.
I think you may have the door on the wrong end of the feedback xfmr primary, but xfmr dots make my head hurt.
I think the dots are fine. When current flows into the dot on the primary the secondary current has to flow out of the dot to balance it. Or if you prefer to think of voltage, when a positive voltage is applied to the dot on the primary then all the other dots will go positive.
When I did the refit in my shop to remove ballast and install Led tubes, I carefully looked for ones with good reviews and hopefully aluminum backing for heat sinking. I installed my Hypericon tubes 6 years ago and the only failure was because one of the tombstones broke. Other than that they have been great.
Note the frequency is always highest, when the oscillator is unloaded, which will cause the impedance of that 4.7nF capacitor to be very low. The frequency drops, once the tube has struck, causing the impedance of the capacitor to increase, so it draws negligible current.
It's the inductor in series with the tube limits the current through the tube, rather than the feedback winding. It will have a higher impedance, to the higher frequency, before the tube starts, so perhaps it's selected to form a resonant circuit with the 4.7nF capacitor, which will increase the current and voltage during start up.
When you said initially that you couldn't see any obvious current limiting, I immediately pointed at the feedback transformer, think "I bet that's it" though without any tangible proof. Your analysis confirmed that you thought exactly the same, but this time with evidence.
Ya, and possibly the capacitor that is in series between the two tubes.
The series capacitor between the electrodes is purely for the heaters. Once the tube has struck it will conduct mostly across the outer terminals.
@@bigclivedotcom I think the tiny capacitor is also needed for startup. Without it there'd be no current path through the feedback transformer.
In my workplace we have backlights for movie posters... actually the frames have been designed by my boss and welded together by is brother. Essentially the frame is 1m high and 0,6ish wide, and the poster is taped at the corners to a 1 x 0,7m piece of 3mm semi-opaque plastic sheet that is forced between the frame sides. There are two 18W fluorescent tube fixtures in each frame. We have been using LED replica tubes in them with great success.
Years ago the LEDs were rather expensive and everyone was already trying to get rid of the fluorescent tube stock. A "general store" of small hardware, household goods, decorative items, and a plethora of utter rubbish, which I very much liked (the store, but the rubbish too) was changing owners and they had huge discounts on some stuff. I saw a shitload of 30W fluorescent tubes sitting in a corner, sold for 0,20€ a piece, and it got me thinking... they were of optimal size to illuminate one poster frame with one tube, without making a brighter spot in the middle of the poster. BUT! And this is a big but! I tried to find prices for fixtures that took 30W tubes, and found out that the store had none, and in general, that size was virtually unobtainable or cost an arm, leg, and some other appendages.
Years ago, there was a term used for any start-up circuit for these and inverters, which was called a "tickler circuit." The switching transistors were tickled into operation.
My employer appears to have a policy (or the contractors that do the work) to replace fluorescent fittings with LED equivalent fittings on failure only. Unless in customer and public areas, where they fit the dim/bright sensor LED fittings. These change to full brightness when they detect movement, then after a while go back to their dim mode. Occasionally (such as in stairways) they use LED fittings that also have movement sensors (radar type, as they can detect through walls) that switch the LEDs off completely if no movement has been detected for a while.
I used to do maintenance for bp oil's head office in Canary wharf. It was mostly fluorescent fittings with with "digital" ballasts(with Dali dimming function). The ballast circuitry was a lot more complex, With a ton of suppression and filter circuitry. The failed ballasts provided me with a constant stream of components to salvage from them. Class XY capacitors for example. My colleagues thought I was crazy for stripping down old florescent ballasts😂😂🤔.
In my experience, LED lamps fail due to the 400 volt filter capacitor going open. If you don't abuse them, LEDs will last a long time. though maybe not as long as a good quality flourescent fitting with a conventional ballast. Replacing the tube is easy and cheap. With electronic ballasts the tube usually outlives the ballast. I think modern LED lights are getting more energy efficient than their counterparts, so I'm not getting any more CFLs. When they go they are replaced with LED equivalents.
I always like your content, Clive, and although I'm an old hand I still sometimes learn something from you. Keep it up!
Almost identical to the circuit used for the old 12 Volt halogen lamp electronic transformers. Think of it as a half bridge and if you scope the output you will see trains of high frequency triggered by the diac at a much lower frequency. Not sure if it was intentional or happened by chance, but, due to the action of the toroidal feedback transformer, you need to give it a load before it starts to work. After that, it only supplies as much power as you pull from it, hence the misquoted power factor figures always given with these devices. Big problem is that as the tube ages, it pulls more current and the switching transistors tend to go off with a bang.
Thank you Clive!
My flat in London has TWO fluorescent lights - a little square one in the bathroom and a “normal” 4 footer in the kitchen. Kitchen recently (2 weeks) needed a new starter…
Thanks for reminding me I need to do something with a light fixture with a dying ballast in it. *OMP* Okay 90 minutes later and I've found appropriate LED replacement tubes with the needed parts included for the retrofit. Only $21 for each kit so for less than $10 more than a new ballast and tubes I can retrofit both fixtures.
Old ballast for fluorescent tubes lasted decades. On the other side, I have a bunch of these electrochinese things that have failed. Have replaced them with LED tubes (that fails fast too). The few of these electronic ballasts that still works burns (literally cooks) tubes in less than a year.
Screw all of that "sustainable" crap. I've scored a lot of vintage industrial fluorescent fixtures (the long tube flavor) in a dumpster, and I will put them in good use replacing the modern ones...
(also old starters makes the random flickering lightshow when turned on, especially satisfying when there are many turned on at once)
I think the two 680 k and 1 nF help with the diode's reverse recovery time. I also think the electrodes will stay hot long enough for the plasma to drain the filter caps to a moderately safe level... the oscillator is still powered after all.
I have changed all my lights to LED 4 years ago. I bought an assortment of new incandescent lightbulbs and put in storage in case I needed some for a heating need.
Half bridge auto generator (electronic transformer) the 1n cap and resistors are to probably fine tune the frequency or add a little dead time. 👍great video as always Clive
Steve
The vans used by (the UK) post office trains use to use 24V DC electronic ballasts to drive the fluorescent fittings on these trains. The reason being that the vans used a 24V DC electric system. I don’t however know what size/type the tubes were (they were all smashed up on the van that I saw, thanks to the vandals).
just got to Edinburgh to vising my brother who's at the uni, just wanted to give a shout and say it's beautiful up here, I am astounded!!
It is very stylish. Remember to check out the spooky Greyfriars graveyard.
Best circuit. I wonder if that pink capacitor couples some mains-derived voltage ripple to the base circuits to help sync the oscillator frequency to a multiple of mains frequency.
Not saying they were identical to these, but these cheap Chinese ballasts caused so many fires in Afghanistan. When I got to Herat, I had to implement some basic electrical safety standards and specified all ballasts must meet CE standards at a minimum... So they found some of these dodgy ones with CE labels of varying authenticity (which isn't uncommon as I've seen even name brand devices with improperly formatted CE logos). Our better contractors at least got Turkish made ballasts.
I have a CFL box for curing resin (nails and other stuff), and when I got it, I checked if it works and then disassembled to see what's inside.
It happened many months ago, but as far as I can recall, it has a tiny microcontroller (for timed mode), and an oscillator circuit, some capacitors and a three-winding (IIRC) inductor on a ferrite bead.
I had no idea what was the circuit, but now it feels like it was something similar to what you showed here.
It's very similar, but usually has one inductor per tube running on a common switching circuit. I took a four-tube one apart in a video.
Nice explanation. Looks like if you installed a jumper at Bx it would allow operation from 120VAC - voltage doubler- (or blow it to h-e-double-hockey-sticks on 240)..
I use Fluorescent Lamps (a two tube fixture) in my garage. I just changed out the factory ballast last year -- the original was installed in 2004.
I actually kind of wish I had another one, tbh.
You may be able to find old stock on eBay.
Have a tridonic ballast which has failed, both transistors(3DD4244D) blown, carbonising around mains input fuses, neutral fuse open circuit. Do you think i would be able to just replace transistors or maybe another component has caused this?
It's possible that the diodes at the input have been damaged too. It may be easier to get a new ballast.
Being less than young, I remember the horrors of the nasty tar filled transformers in the original fluorescent fixtures that often ended their life with a burn and smoke. The testing company I worked for was in the basement of an old bank building with questionable air movement, having one of these things go off was a Chernobyl quality event. A smell that you can taste... ah the memories.
I still have a fluorescent t8 lamp in my bedroom, no fixture, just a 120v ballast with a single wire going to each end of the tube, it drives it like a ccfl without touching the filaments so it has been in operation atleast 10 hours a day for the last 10? Years, the only non compact florescent left in the house i think? As bulbs have been burning out I've just replaced the fixtures with Edison screws so i can pop LED bulbs in as they are needed or even incandescent if I'm feeling naughty or need an additional heat source for specialized purposes
In addition from another comment thread, My favorite has discharge lamps all use metal salts and a very hot arc, 1000 watts of limited band orange light is so lovely, reminds me of sweet home Chicago, you can always find your bearings just by looking up at the clouds and finding the orange glow, sadly the glow isn't as orange anymore because of the trend for LEDs replacing them, i still want a low pressure sodium lamp.... Never got my hands on 1
In the lift industry LED is taking over but I’m not sure if cheap ones are being supplied but the LED kits are learning about 6 months rather than the amount of years the old fluorescent ones did
A lot of LED lighting fails fast. And it often requires the whole fitting to be replaced.
I had a couple of this style of ballast for my fluro lamps before I went LED. They worked but were rough on the lamps, no preheat, just blast breakdown voltage at them. Would have been stripping the emitters for sure. There is one thing i do remember about them though. If the lamp was cold, say 10c or less, you could see the lamps were being run at 10kHz or so by the size of the dim bands running along them compared to how they looked when cold with 50/100Hz.
As some one that spent a large part of my working life dealing with fluorescent light fixtures they were great till the government implemented energy saving legislation. Manufactures had to introduce the ALTO bulb they were hit or miss right out of the box. It got to the point working on a 2 bulb fixture you took 4 bulbs and a new ballast with you on all the work orders. I rip the ballast out swap in retro fit leds now to keep my sanity!
I have two 8 foot fluorescents in my kitchen 21 years on the tubes and still going. Only modern thing is electronic starters.
I wonder if the DIAC startup circuit is why it doesn't need the series capacitor? At startup, both transistors will be off, and no current will flow through the tube. The other style use the noise in the transistors to start the oscillation, and the capacitor might need to be there so it can amplify enough to get it oscillating reliably. That, or it's in that linear region for a relatively long time and the capacitor stops large currents from flowing. In the US, the ballast I took apart works very similar to this; it reminds me of the old AT power supplies using two capacitors, a bridge, and the switch for 120/240 that modifies the diode bridge connection so it either straight rectifies (240V) or makes it into a doubler (120V) and thus the supply runs on the same voltage internally in both cases.
We have both led and florescent lights at my work place. After 20 years I am finally having to replace ballasts. The led lights are more recent and so far only one has failed.
A video before I head to work excellent way to start the day 😆👌🏼
The board would benefit from a fusible resistor on the input.
Thank you very much for this, I couldn't understand how the feedback transformer works when I tried to fix a broken lamp. (There are a UV lamps out there that still use those).
That power supply was on the kind of a a circular custom-shaped board that would fit into the base of the lamp. It had a similar design with a couple more transistors and diodes here and there.
The electronic ones I've opened were filled with potted black stuff, covering all the components. I've slowly replaced the ones in my garage with direct wire no ballast needed L.E.D tubes.
Clive, have you worked with 12v fluorescent light ballasts for 40 w? They are typically used in caravans and food trucks.
They're often based on Royer type oscillators with auxiliary windings for heating the cathodes.
I am retired now but I was asked to increase lighting in a liitle used room, I was going to fit LED light and I was checking wholesale prices and I found I could buy a twin 4 foot fluorescent fitting including tubes and VAT for just over £5:00. Figured the payback on LED was abot 10-15 years so went fluorescent
I had an actual 4ft fluorescent tube in the basement go dimmer... and dimmer... and dimmer... 'til it barely glowed. Replaced it with a new bulb, which was nice and bright... for about a week, then went dim again. Got a plug'n'play LED stick (ie, no need to remove the ballast and/or rewire the fixture), and it's chugging along nicely for about a year. Nice 4000K, and not eye-scorching 7000K anymore. Did the same for 3ft tubes in the kitchen above the windows.
I have fluorescent lights in my garage - one failed recently and I'd been considering changing to LED strips, but then someone on Freecycle was giving away a dozen fluorescent lamps exactly right for my garage! So that's me sorted for the next fifty years...
This reminds me of an electronic ballast I found in an unusually cheap and lightweight residential high-pressure-sodium yard light several years back when I was collecting HID lighting fixtures. Unlike most of these luminaires that used conventional iron ballasts, this one had a single rectangular board inside with all the componentry built on, including the photosensor for dusk-to-dawn operation. Mostly discrete components with maybe an IC or two. Makes me curious how similar it is to the fluorescent lamp ballast circuitry.
The 50 watt hPS Lights Of America Model 9051 "WallPack" ?
I have the 42 watt CFL version (Model 9042) that I converted to house an 18 watt Low Pressure Sodium (SOX) lamp. The schematic for both the fluorescent and the HPS versions are published on Sam's Repairfaq
@@yuandrew Yes, I think that's the one! I didn't know they had schematics on Sam's site. That's pretty cool. We may have had the fluorescent version too. Problem is, it seems like most of LOA's products always had QC issues. Both the fluorescent and HPS units died shortly after we got them. Our replacement HPS unit finally managed to outlive its lamp, and was still working the last time I plugged it in.
Nice a ballast video ! I really like fluorescent lights and love them when they start to flash before dying. But sounds dangerous this ballast and cheap
Was trying to diagnose somebody's ring light. It happens to be a ceiling fan that uses a fluorescent tube in a ring, I've only ever seen this once. They bought an LED retrofit which slightly doesn't fit the tabs that hold the bulb in. And in an attempt to figure out why it wasn't working I bypassed the ballast and blew the internal fuse. Apparently they never intended the unit to be direct wired. annoying because the ballast in the ceiling fan was bad after diagnosing with a known good glass bulb. And no not necessarily standard as in no standard light sockets it had a prepare pin snap in design. And ceiling fans are notorious for not having any extra space.
i could be crazy, but it doesn't look like that green deal between the two smoothing capacitors connects to their output, the orange circuit. if you ask me it pretty clearly goes from the red circuit to the pink circuit.
Fluro lamps typically need a ground plane in order to start ( capacitance effect ) I wonder if this circuitry eliminates that need.
I think the ground plane (or even just the cables running along the tube) would be needed for reliable starting.
is this what you mean with not being up at sociable hours?
There's a certain type of electrical engineer and/or technician that would love to work 9 to 5, but pm to am. I wonder what that's about...
Didn’t think there was a need for these still, nice tear down Clive thanks
Very nicelylayed out board.
I have some really old fluorescent fixtures that have the super old ballast's in them. The big heavy ones. For some reason I've never been able to wrap my head around how a ballast works. I know why you need them. But I don't really know how they limit current.
A resistor can be used to limit current and that's what _ultra_ cheap fluorescent fixtures use. Regular series-connected magnetic ballasts are just inductors. Inductors have an impedance to AC so they basically emulate a resistor without wasting all the power. More advanced "rapid-start" ballasts were standard for longer tubes in the US and they are basically step-up transformers with leakage inductance.
They're less and less but some places still have fluorescents. We did until they stopped selling fluorescent tubes and came out with the universal drop-in ones that don't require rewiring... Although even then I waited until the tubes were getting dim and needed to be replaced anyway. I'd love to know how the drop-in replacement ones work that are compatible with T11, T8, and direct wire without any modifications. Unfortunately I learned they are real glass when one broke so it would be a major mess to tear one down and reverse-engineer.
All the Ballast I have installed are potted in Resin. I guess they don't do that overseas?
I'd use that ballast! 40 watt 4 foot tubes are super bright now, and have a nice color rendition compared to the old days. I have a "vintage" dual tube 4 foot fixture in my walk in closet but it's still using the old purely inductive ballast which gives that nice growl sound.
The hum was sometimes nice and sometimes way too loud, i recall moments from school where we loudly hummed when teacher was talking and then blamed it on the lights.
@@plainedgedsaw1694 If the ballast in my closet gets that loud it's going on the curb on trash day. In the 9th grade the public school had big incandescent bulbs. I couldn't believe it. They didn't flicker or hum though. On warm days we turned them off and relied on natural light to keep the room cooler.
Isn't the 1n cap just there for pre-heating the filaments? I can't see any other current path till the diac breaks over causing the lower npn to switch.