One of my patrons asked if I still had the old broken parts from the smashed KV-9PT50 I had on a previous video. Unfortunately, due to space constraints, I didn't keep the parts.
Oh, you should have kept at least the flyback, the vertical output IC and the horizontal output transistor, if not the whole chassis. Those are the most common failure points, and none of them available.
@jamesrowden303 I 100% support whatever he wants/wanted to do, but as to "no" point: if it's something you are absolutely sure there is an immediate market for (few to none on ebay, high sale price and short listing times on completed items) there is a point to some of us. I have literally zero "storage" space available but if I knew something could turn into $100 in a couple days I'd certainly let it rent a couple square feet of my office desk.
@jamesrowden303 Yes, but he clearly has at least one of these TVs that he intend to keep. If the flyback fails in that, game over. A flyback and a few ICs don't take much storage space. When I come across something that is beyond repair, but it is either a generally highly sought after set, or I want one myself for my collection, I always keep all the critical, otherwise not available parts from such units. I just bought today a nearly 50 years old Sony PVM-1300 Trinitron monitor. It works fine, but I might end up buying an other one with weak tube from the same seller, just for a spare flyback and knobs (one knob is missing from mine).
If you need parts, I have one of these that works flawlessly, but the plastic shell is cracked pretty bad. It needs a new shell. I'm not a patreon or anything but I like to help
Check the safety circuit, it could be shutting off the TV. Example if you have a bad capacitor it could put the Horizontal frequency way off and the safety circuit will kick in. In the drawing you should see a line going to it from the flyback transformer monitoring the set. I think it is kicking in before all the rail voltages have time to come up to the correct levels. This is a common issue on older sets. They put these in place and that is why they do not have all the metal shielding like the older tube sets had. Also note that you did have somewhat the correct horizontal frequency on startup but it could be drifting off when it gets all the power rail and the other circuits start up. A short in one of the could also kick in the safety circuit. Sorry for the long comment.
A set shunting down like what you are experiencing usually means one of 2 things: 1) X ray protection kicks in (over voltage condition in the high voltage) 2) An overload in any of the branches powered by the flyback transformer The squealing sound would seam to indicate it is the second option but the first one cannot be ruled out completely. Usually the outputs of a FB transformer should look like a 40% duty cycle square wave with 0v in the middle so the same output could produce both positive and negative voltage depending on how the rectifier diodes are connected. Also a FB transformer is a current transformer. the output voltages depend on the energy stored in the core when the primary side current disappears. An overload on one branch will "sink" the voltages in all other branches. I hope this helps, keep fighting ...
Don't forget to check the resonant capacitors in parallel with the line output transistor. Seen those go bad many times. Usually if they're bubbling or bulging it's a clear sign of a defect.
My only notes for this set: R501 and R502 open up - "squedging" (Dad's words for non-standard squealing) and no scan-derived supplies. Both are 10K, surface mount. PS - Dad was a TV repair tech for 52 years.....he left tons of notes for sets, many now in landfills. Personally, Sony horizontal driver transformer solder connections are ALWAYS resoldered. Helps prevent callbacks.
As an expert in both CRT displays and transformers, I will offer some suggestions to consider. First thing I would try is to disable the protection circuitry that shuts down the horizontal output and high voltage. Before powering on in this mode, be monitoring the CRT anode voltage and at least one of the other secondary supply voltages on the flyback; you don’t want excessive voltage to fry anything. If you have a variac, it might make sense to use that to slowly bring up the AC power voltage. As to the theory that the flyback may have internal shorting that only appears when the voltage is high enough, this is a possibility. What I have found from experience is that even ordinary switching power supply transformers can do that too, so it’s not far fetched. We actually had that happen quite frequently with switching power supply transformers, to the point where we developed a test circuit that used a horizontal flyback type of circuit to apply more than twice the expected voltage to the part, and that would be observed on a scope for a minute; bad parts would fail quickly, good parts would last in the field. We stipulated that this test be performed by our transformer manufacturers. Our one transformer supplier even contacted me saying they would always have a percentage of transformers fail, but when ours failed they failed at their factory and we weren’t returning failed transformers for that reason, whereas other customers of theirs had them failing in the field and they would get a bunch returned. He wanted to use our test for all of his customers, and we obliged them by supplying the design details. And he said once they implemented that, failures in house before shipping increased but returns went down - that’s what they were hoping for. So back to shorting / arcing under high enough voltage. Obviously you can’t give this flyback double voltage like my test did. But you can keep it running if the shutdown doesn’t happen, and if it is arcing eventually that will char the internal insulation to the point where it conducts and that will accelerate the failure. Likewise if there is a situation such as what we had with ordinary power supply transformers - there would be small pinholes in the magnet wire insulation, and when two pinholes on adjacent turns of wire got too close that turn of wire would be an effective shorted winding on the transformer, and the transformer is useless / worthless for continued operation.
Another observation is related to the waveform on 12 V secondary winding - it has notable -40 V dip downs that caused by a back EMF that occurs when the power transistor in the primary naturally cuts off on every cycle. The significant amount of that back EMF signifies that the transistor in the primary section puts a lot of power into the coil, but it doesn’t come through as expected. Once again, that’s a sign of overload in the secondary section, but surely it occurs *after* the rectification. For example, if it was a short circuit inside the transformer then you wouldn’t have back EMF spikes so big.
I'd check the line output txfrmr primary drive circuit, it maybe working overtime due to an issue with the drive transistor and hence the squealing. Just a thought and give it another go Adrian, LOPT's are usually really reliable in smaller sets due to a lower high voltage output than bigger sets. Great video btw!
I have a good friend, who has worked on TV's professionally for many years, dating back to 'tube' populated components in the sets. Based on what he's discussed, if the FlyBack Transformer is failing or 'breaking down' under high voltage load, the TV is designed to shutdown, for safety reasons. Part substitution would be the next step, if parts were still available. As he has said the failure of a Flyback Transformer can be a show-stopper.
High pitched squeal with shutdown- definitely characteristic of a voltage rail overload. You've done your due diligence checking the usual problem areas and components, and without pulling that flyback and performing a ring test I'd be writing it off as the culprit as well. You would have been lucky to find a replacement fly for this set ten years ago, and even then most of the market had been proliferated with poor quality generics that usually either didn't work out of the box or didn't quite fit the PCB footprint, on and on. Long Live SORNY!
Always save the flybacks out of old TVs when you get rid of them. I do. There is a project to make a universal flyback transformer, I watched a video about it on RUclips. As someone who fixes old arcade games it is really interesting to me. Looking forward to a Coleco Adam video in the future.
The idea of a “universal flyback transformer” is a pipe dream. The secondary output voltages that feed circuitry other than the CRT anode will vary from model to model. The resonant circuit will vary from model to model. Sets with larger CRTs usually need higher anode voltages. If a “universal flyback transformer” was remotely possible, the manufacturers would already be using the exact same flyback transformer across the board - that improves “economies of scale” (saves money so more profitable to do). The flyback manufacturers offered standard catalog models in the hopes that set manufacturers would use those, and they all had several of those standard catalog flyback models. So don’t hold your breath waiting on one of these.
The TV squealing and shutting down means that the protection circuit is working and cutting down power to avoid more damage. One strategy to figure out why is usually disconnecting each power rail one by one (disconnecting the diode for example) to see what happens and define on which rail the problem really is. Another possibility is turning off the protection circuit and connect it to a power limiting circuit (serial bulb) to see what gets warm for example, but that is a bit more technical thing to do. Another easy alternative is you feeding low voltage through an external power supply and check for heating of parts. I guess that is the safest, does not harm the circuits and you would circumvent the protection circuit.
The TV horizontal drive circuit is pretty much a big SMPS with a feedback loop. It tries to start the horizontal drive and if it doesn't see the right voltages on the power rails within a few seconds, it will shut down. There's also a protection circuit that trips if the high voltage becomes too low to prevent the TV from generating X-rays.
@@Stoney3K could be fault in line out or psu stage, i had a sony kv1442 that would go unstable and squealy, it was a 'noisy' zener in the psu,, i have an ancient sony kv1300 that does similar but psu in that seems ok, i havent investigated that one further yet
@@s8472-k8i A TV will generate X-rays if the high voltage becomes too high (around 25-30kV for most tubes) because the velocity of the electrons hitting the phosphor is too high.
Something else to check for would be corona discharge. Turn all the lights off to make it as dark as you can and turn the set on with a clear view of the flyback. If it's a insulation issue (HV leak) you may be able to see the blue/purple arc emminating from around the flyback.
While the flyback ring testers are not definitive for testing good, if it says it's bad, it's bad. I'd suggest getting one. They can spot a single shorted turn where your multimeter can't tell. And they're not hard to operate.
Based on the symptoms, I would guess that either the driver side is weak or some monitoring chip isn't getting the right "it did turn on" signal. Because the outputs all show signs of "getting up there" before it drops down again, I would primarily assume that the flyback is at least almost fine. There might be a high voltage breakdown, yes, but I think the waveform would look slightly different, more like a rising sawtooth than what looked - from afar - like a symmetrical up/down spike... I'd check up on the input drivers next: a.: do the 5V remain stable during power up? Firing that primary coil up takes quite a bit of current; if the main filter caps are weak, maybe the 5V logic voltage has a droop and that causes a reset in the control chip? b.: does the switching transistor "behave"? i.e. is it turning on and off completely and fast enough? Compare base/gate signal to the output towards the primary coil... I had a slightly larger Sony set where the Flyback was knocked clean through the PCB during transport. Tose things are sturdy. Not a huge Sony fan myself, but the TV sets they made were tanks with screens as far as I can tell.
I suspect the driver side is current limiting due to a overload. And I think the safety circuit is doing it's job as the voltages never get where they should be.
How ironic... Back when I was a kid, there were commercials of tv repairmen coming to your house to fix your tv. $39.00 later, they would leave, with a smile on everyone's face... Now, it's hardly an option at all, to have your tv fixed . .. Good thing the videos make money! 👍
I think somebody suggested ringing test for the transformer. That probably related to a Sencore Capacitor-Inductor Analyzer. One of their models was (or is?) LC102. It applies an impulse to a tuned LC combination and counts the number of the decaying ringing waves. It is an indicator of the Q-factor of the inductor. Easy and simple result, without math or any deeper understanding of the L-C-R circuit analysis. However, the (already shown) DER EE instrument DE-5000 can also be used. In this case I would measure the inductance and the Q-factor at 10 kHz, which is closest to the nominal 15.75 kHz use of the horizontal deflection.
Squealing usually signifies a flyback transformer overload. I remember when my father accidentally short-circuited the flyback output, the transformer went squealing like crazy. I even thought it turned into a whistle for a brief moment. When the overload condition was fixed, the transformer started to work as usual. But it look has changed: it became a slightly more brownish color than it was before the overload.
Been there with an early 80s Sony KV2204UB set, about nine months in the LOPT went causing a squegging sound then shutdown. The original LOPT was a UK made part, a Japanese part was installed and saw the set out.
As I remember the Sony sets, they have a lot of protection all arround,so in most cases the sets shuts down. Well, its seldom that Sony flyback trafo goes bad, but of course this could happend. Have you checked the safety resistors on the powerrails they sometimes raise in value, also when you start up and power down the unit, there are a poping sound in the speaker, perhaps the main audio amp are shorted from power to output, normally its a differential amp between 2 powerrails. Keep up the good work
try disconnecting all those power lines from the lopt , so nothing is loading it and see if it powers up , also check line driver stage before the line output transistor
Earlier this year, our Bomb Jack cocktail table arcade machine monitor broke. It turns on for a split second, generates high voltage and blows the fuse. Powering it on on a variac, at 40V you could see smoke from the flyback (it's a 100V monitor). Sad. It's one of those unobtainium flybacks, but there's a nutty professor TV serviceman in my country who's working on something that resembles a universal flyback to flyback adapter, read that as "you can put any (similar-ish) flyback in any monitor with this one trick". Would be cool, that monitor had a bright and vibrant picture despite massive burn-in.
I don't think the flyback is at fault here. Seems to me like the IC that generates the horizontal pulses has a startup mode and a run mode. All the voltages start coming up quickly at the beginning, so the startup seems to work. Maybe the horizontal pulses go bad when the run mode engages after the voltages have come up enough? i would look at the horizontal drive on the scope with a longer timebase to see how it changes over time.
I remember Shango66 having problems with the power supplies on old Sonys. I think they have an unusual feedback loop power supply and problems with cracked flybacks. Just an idea.
At your local garbage dump, in their recycling section maybe someone plopped one off there you can use for parts? Here in PA, they don't care if you drop off electronics and take anything you see (free to drop off and take - lol). I also have a buddy in the business with almost three stories of part TVs, I asked him if he would have one for you.
Hi Dude, that is very interesting. I have the same problems. I would like to continue to repair such devices in the future, so I like to follow such videos. I had asked a lot of older TV service men if they could help me, but everyone ran away and they said they were glad these tube tvs were over. In fact, it is relatively difficult to repair such tv. For reasons of economy, everything is related together to one thing: flyback transformer, deflection, etc. Well, either everything works or nothing works. It can very well be that the flyback has an internal short like an insulation failure, that often happens. I'm not sure it is a good idea to power up the device while the neckboard is disconnected. The ground is interrupted and this is to be avoided. Well the tube is not conducting when not heated, but note that the tube is a capacitor, so theoreticly once a high voltage can come out on the socket pins of the tube ?
I agree most likely the fly back transformer, no obvious shorts, could be worth checking, there's usually a capacitor across the line output transistor, between the collector and emitter, about 7n depending on the screen size, I have had this fail on occasion, but really the sequel noise says it all, a shorted winding inside the tranny, seems a shame to give up because the condition of the set looks pretty good.
I remember around thirty years ago there was a device you could buy that could test for any shorts inside a fly back transformer, maybe there's a schematic somewhere online, probably some sort of simple oscillator circuit involved, could be worth looking into for future repairs.
@@BlondieHappyGuy Probably the best option, I don't see why it wouldn't be the same, unless the design is radically different to the AC version, I know some older Hitachi sets used the same fly back between the DC and AC only sets, easy to pop off the back and check see if the number matches.
This looks more like one of the secondary load circuits being shorted. If the flyback was bad (shorted) the horizontal output transistor would likely be fried.
@@stevebabiak6997 It does look like there is some sort of loading going on, whether its the transformer or something in the secondary, I was under the impression that a short in the secondary was mostly eliminated, Although the line output transistor can get damaged, I've found in the past not always, depends how quickly the power supply responds, Maybe something in the power supply itself, there is usually a cap around 47uf 63v in the primary section, when it goes bad it can throw you off thinking the problem is due to a short, In the end, it's a great help if you can replace and rule out the transformer if things get difficult.
@@electronicarchaeology - using “shotgunning” by changing the flyback isn’t something I’d recommend. They aren’t a regularly stocked component at the typical distributor, and they are expensive to boot. If he can even find one. I posted a lengthy top level comment giving some ideas. IMO if that flyback is kaput then that set has now become a parts set to cannibalize for the next similar set.
@@stevebabiak6997 You're mistaken there's no shot gunning as you call it involved, if you watch the full video Adrian mentioned that he had another set, A 12v version, if a service engineer suspects the fly back transformer and has another at his disposal, There's nothing wrong in swapping it out even if it for elimination purposes, I've been a service engineer for more than 40 years, my colleagues and I have done this many times.
2:03 THANK YOU YES I heard it thank you for reminding me that my hearing isn't as destroyed as I thought it was! oh wait. it's still there, and it's like 2:58 now. it's permanent. it's worse than I thought. Oh well, thanks for trying. I just checked to make sure your videos are captioned. If they weren't we'd need to get that set up so I could keep watching your videos!
The one site that I saw that had this part listed (out of stock) had it for over $70. So probably the best way to do this is to go to an electronics recycler and see if you can get a TV there for parts.
Dude...they don't have be great videos, they have to be Adrian videos...that's why we watch....in this crazy ass world all i can say is, please just keep cranking them out....i hide in my basement and try to repair things too and stream of concsiousness is pretty much the only mental process i use
I had the exact same TV in my kitchen for many years back in the early to late 2000's. It failed in the same manner. I'm into electronics and finally scrapped it. I DID save the picture tube though, it's a pretty advanced tube and I figured someone maybe could use it in the future.
CORRECTED EDITED TEXT: ; Do not work on CRTs unless you know how to be safe! ; ** Today on the bench we have a little SONY TRINITRON ; that has a fault where it squeals and then turns OFF
That set reminds me of the little Aiwa we had in the kitchen for a bit back in the 90s/00s. Not sure what happened to it. Seems like a lack of replacement flybacks is what condemns a lot of CRTs to the dump these days.
The side tones kind of makes me suspect there's some resonance fault in either the flyback or the yoke, as both are needed in creating the 15.75kHz resonant tank circuit. It could very well be a magnetic circuit failure (so not an electrical one) in the flyback.
Not every day the thumbnail features a grumpy looking Adrian… my next step would be to locate the shutdown circuit and see if it’s getting activated and start from there.
Would it help to lift some components so to disconnect the flyback from the rest of the circuit and see if voltages run fine (for as long as the TV stays powered)?
that high pitched whistle? I hear them all the time on Bob Anderson's channel when he fixes vintage tv's the only spare tube tv stuff I have laying around is some parts from an old portable set
Two places you would find a TV like this in the 90's, Yes a Kitchen or a Teenage Girl's Bedroom. TVs like this have even been featured, in the background of, Movies and TV Shows.
Check the primary side of the flyback transformer and the drive circuit. Disconnect all secondary loads (remove rectifier diodes) and see if anything changes. Could be a bad cap in the primary or secondary.
When doing any troubleshooting, or science in general, only EVER change one variable at a time. Because if you change two or more, and the system starts working, which was the problem? Half splitting is good, but only if you can isolate one half or the other as the fault. I.E. only one variable.
High pitched squealing can indicate a faulty flyback TX. It would certainly be the next component to eliminate if you can get one from somewhere. Wow it doesn't seem that long ago since I was replacing them, but with the dominance of LCD and OLED displays there's not mutch of a demand for them to justify manufacture 😢
I wish a brand out there would make a modern CRT. Imagine the space savings using newer micro technology. Reduce the mainboard by 3/4ths making it 1/4th the size we see here. And add hdmi/dp along side the oldschool connections (rca, coax, component, bnc, etc). With modern tech i bet we could make 240hz crts which would be insane for modern pc gaming
Nice looking little TV - had a quick search on the UK Ebay pages and sadly I don't think we got it over here. Pity as it would make a nice little TV for my one of my retro setups.
Test the OpAmp. If I'm not mistaken part of the drive signal goes through it. If it's just part of the audio circuit then it likely has nothing to do with the issue. That's where I'd look though.
Squeal and shutdown is a fairly good indication of an overloaded power supply, so something on the main bus is likely a short to ground. Hor Output device is a usually a good start. Most Sony's used a Gate Controlled Switch vs a bipolar power transistor for that one. EHT tranny or vert o/p is also possible.
Sometimes failures can occur due to poor storage, humidity, etc. I suppose cracks can also happen during transportation. Not *all* faults can come from "normal use", I guess.
The obvious one is glaring.. C515 along with the diode D504 going leaky.. Also the cap C516 in my experience is a source of trouble on these circuits. Not a common set here in the UK at all.. but there was a good reason I didn't do Sony Trinitrons back in the day..
I had a similar set, black, and the symptoms were also similar. It ended up being the flyback. I managed to get a replacement, but it was 10 years ago. Maybe shango066 can help you with one. He also has a Sony repair video with a strange behavior caused by a flyback.
i do remember one thing about it cuttting off it is because there short somewhere liar in capacity check voltage rails by transfer and see if any voltage drop if yes and there issues in rail to something that shorting it im sure you will find it if you start at beging where power come in and i do believe there just that you over looked it go back and check it
Try to desolder H-OUT pin of flyback or desolder horizontal out transistor and then try to turn on the set. If it will not squeal, then it's high possibility that flyback is bad.
I took electronics repair as major in high school, but that was half my life ago. My guess would be as you suspect an internal issue in the flyback xformer, or maybe the drive circuit for it?
At 2:15, your spectrum analyzer app showed peaks at 10.5 and 5.25 kHz, which are harmonically related to the expected 15.75 kHz. Maybe why the squeal seemed loud: the ear is much more sensitive at the lower frequencies. But I'm wondering what that tells us about the problem? Maybe the problem is on the primary side, in the horizontal drive circuit?
I deliberately haven't yet watched the video because its asking to guess how this repair went. The facial expression suggests that Adrian is almost annoyed. Given that its a CRT I'm going to guess you stopped it shutting off and then it tried to destroy itself. Its had enough. I have had a few interesting moments with CUB microvitec monitors that have just had enough of life. They fight and bite you like taking the cat to the vets.
I may have missed it but I didn't see the output voltages and wave form of the main PSU output being checked during power on. If the main PSU is failing to maintain the B+ at an adequate voltage under load it could easily cause the flyback to and horizon drive to shut down, and cause the low HT voltages as well. I'm sure you have done this already, just off the video. Can't you cut the traces on the output side (+/-12 etc) of the flyback to isolate them from the circuit and see what waveforms and voltages you get off the windings?
Both 12 volt rails and the high voltage are all around 1/3 what they should be but you said you don't get anything on the 180 volt rail. It seems to me the problem is then with the 180 volt line. If disconnecting the neck board gives you confidence the problem is not after the rectification then logically the rectification stage itself could also be the problem. You didn't test that diode on camera and even if the forward drop is okay it might be breaking down under higher reverse voltages. If the diode is bypassed by a capacitor that could also be faulty with voltage.
Why didn't you try to desolder the +12v and the -12v pins from the transformer to isolate them from the circuit? You could have seen if it was the transformer. OR (I guess) you could have tried to understand where the hissing sound comes from with idk a good microphone? It would have lead you to the problem
Sorry Adrian, fell asleep mid video, but the sound described sounded like a tripler failure. Seeing 1/3rd of the voltage I would expect on the tube ..... Did you say you have another of these TV's you could borrow from?
Hello I can help you on this repair Put you scope on collector of Hoz out transistor collector and you should see a clean pulse with no hump If it is clean you have another issue like the la7830 is bad. I have fixed tons of them in the day
![Adrian's Digital Basement ][](http://yt3.ggpht.com/ytc/AIdro_k7CrQRe71qN6c0Ua7A1P_I8KkxjqLa70u0zYeCvdvnKw=s48-c-k-c0x00ffffff-no-rj)
![0096 Giving my Apple ][+ multiple personalities with ROMX+](http://i.ytimg.com/vi/9EDtnLRuFuU/mqdefault.jpg)
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One of my patrons asked if I still had the old broken parts from the smashed KV-9PT50 I had on a previous video. Unfortunately, due to space constraints, I didn't keep the parts.
I bet Adrian has a logistics manager employed full time ;-)
Oh, you should have kept at least the flyback, the vertical output IC and the horizontal output transistor, if not the whole chassis. Those are the most common failure points, and none of them available.
Oohhhhh.... i was going to ask the same thing.. 😶
@jamesrowden303 I 100% support whatever he wants/wanted to do, but as to "no" point: if it's something you are absolutely sure there is an immediate market for (few to none on ebay, high sale price and short listing times on completed items) there is a point to some of us.
I have literally zero "storage" space available but if I knew something could turn into $100 in a couple days I'd certainly let it rent a couple square feet of my office desk.
@jamesrowden303 Yes, but he clearly has at least one of these TVs that he intend to keep. If the flyback fails in that, game over. A flyback and a few ICs don't take much storage space. When I come across something that is beyond repair, but it is either a generally highly sought after set, or I want one myself for my collection, I always keep all the critical, otherwise not available parts from such units.
I just bought today a nearly 50 years old Sony PVM-1300 Trinitron monitor. It works fine, but I might end up buying an other one with weak tube from the same seller, just for a spare flyback and knobs (one knob is missing from mine).
If you need parts, I have one of these that works flawlessly, but the plastic shell is cracked pretty bad. It needs a new shell. I'm not a patreon or anything but I like to help
just replying to give it a bump.
Whoop whoop (to bump it up as well)
Up, up!
Bump bump
Bump again
Check the safety circuit, it could be shutting off the TV. Example if you have a bad capacitor it could put the Horizontal frequency way off and the safety circuit will kick in. In the drawing you should see a line going to it from the flyback transformer monitoring the set. I think it is kicking in before all the rail voltages have time to come up to the correct levels. This is a common issue on older sets. They put these in place and that is why they do not have all the metal shielding like the older tube sets had. Also note that you did have somewhat the correct horizontal frequency on startup but it could be drifting off when it gets all the power rail and the other circuits start up. A short in one of the could also kick in the safety circuit. Sorry for the long comment.
A set shunting down like what you are experiencing usually means one of 2 things:
1) X ray protection kicks in (over voltage condition in the high voltage)
2) An overload in any of the branches powered by the flyback transformer
The squealing sound would seam to indicate it is the second option but the first one cannot be ruled out completely.
Usually the outputs of a FB transformer should look like a 40% duty cycle square wave with 0v in the middle so the same output could produce both positive and negative voltage depending on how the rectifier diodes are connected.
Also a FB transformer is a current transformer. the output voltages depend on the energy stored in the core when the primary side current disappears. An overload on one branch will "sink" the voltages in all other branches.
I hope this helps, keep fighting ...
Don't forget to check the resonant capacitors in parallel with the line output transistor. Seen those go bad many times. Usually if they're bubbling or bulging it's a clear sign of a defect.
Statement of the day at 16:29 "there's something in this set that's faulty". Thank you Adrian, that made me laugh :)
My only notes for this set: R501 and R502 open up - "squedging" (Dad's words for non-standard squealing) and no scan-derived supplies. Both are 10K, surface mount.
PS - Dad was a TV repair tech for 52 years.....he left tons of notes for sets, many now in landfills.
Personally, Sony horizontal driver transformer solder connections are ALWAYS resoldered. Helps prevent callbacks.
Would you be willing to transcribe all these notes? I can host them if you desire.
Do you have any notes for a Panasonic CT-27XF14CV or a CT-27SF14CV?
You're a hero for even trying. I'm worried about what we're gonna do when you're not around to guide and teach us anymore.
Adrian is still a young lad! ;)
As an expert in both CRT displays and transformers, I will offer some suggestions to consider.
First thing I would try is to disable the protection circuitry that shuts down the horizontal output and high voltage. Before powering on in this mode, be monitoring the CRT anode voltage and at least one of the other secondary supply voltages on the flyback; you don’t want excessive voltage to fry anything. If you have a variac, it might make sense to use that to slowly bring up the AC power voltage.
As to the theory that the flyback may have internal shorting that only appears when the voltage is high enough, this is a possibility. What I have found from experience is that even ordinary switching power supply transformers can do that too, so it’s not far fetched. We actually had that happen quite frequently with switching power supply transformers, to the point where we developed a test circuit that used a horizontal flyback type of circuit to apply more than twice the expected voltage to the part, and that would be observed on a scope for a minute; bad parts would fail quickly, good parts would last in the field. We stipulated that this test be performed by our transformer manufacturers. Our one transformer supplier even contacted me saying they would always have a percentage of transformers fail, but when ours failed they failed at their factory and we weren’t returning failed transformers for that reason, whereas other customers of theirs had them failing in the field and they would get a bunch returned. He wanted to use our test for all of his customers, and we obliged them by supplying the design details. And he said once they implemented that, failures in house before shipping increased but returns went down - that’s what they were hoping for.
So back to shorting / arcing under high enough voltage. Obviously you can’t give this flyback double voltage like my test did. But you can keep it running if the shutdown doesn’t happen, and if it is arcing eventually that will char the internal insulation to the point where it conducts and that will accelerate the failure. Likewise if there is a situation such as what we had with ordinary power supply transformers - there would be small pinholes in the magnet wire insulation, and when two pinholes on adjacent turns of wire got too close that turn of wire would be an effective shorted winding on the transformer, and the transformer is useless / worthless for continued operation.
Very solid advice. Writing a comment to hopefully bump it up in the comments list.
The X-ray detection circuit is crowbaring the flyback into protection mode.
Where is the X-ray detection circuit? Never heard of anything like that in a tv. When was that introduced?
Another observation is related to the waveform on 12 V secondary winding - it has notable -40 V dip downs that caused by a back EMF that occurs when the power transistor in the primary naturally cuts off on every cycle. The significant amount of that back EMF signifies that the transistor in the primary section puts a lot of power into the coil, but it doesn’t come through as expected. Once again, that’s a sign of overload in the secondary section, but surely it occurs *after* the rectification. For example, if it was a short circuit inside the transformer then you wouldn’t have back EMF spikes so big.
This. Ive seen the HV rectifier diodes go shorted/leaky in the flybacks as well, even doing a 1B3 mod to rule it out.
I'd check the line output txfrmr primary drive circuit, it maybe working overtime due to an issue with the drive transistor and hence the squealing. Just a thought and give it another go Adrian, LOPT's are usually really reliable in smaller sets due to a lower high voltage output than bigger sets. Great video btw!
I have a good friend, who has worked on TV's professionally for many years, dating back to 'tube' populated components in the sets. Based on what he's discussed, if the FlyBack Transformer is failing or 'breaking down' under high voltage load, the TV is designed to shutdown, for safety reasons. Part substitution would be the next step, if parts were still available. As he has said the failure of a Flyback Transformer can be a show-stopper.
Gaaah!!! Never give up Adrian . I hope you continue with this one as frustrating (and dangerous) as CRT TVs are. :)
High pitched squeal with shutdown- definitely characteristic of a voltage rail overload. You've done your due diligence checking the usual problem areas and components, and without pulling that flyback and performing a ring test I'd be writing it off as the culprit as well. You would have been lucky to find a replacement fly for this set ten years ago, and even then most of the market had been proliferated with poor quality generics that usually either didn't work out of the box or didn't quite fit the PCB footprint, on and on. Long Live SORNY!
Should have gotten a Magnetbox instead
@@nilz23 That, exactly. Thank you! 😁
Always save the flybacks out of old TVs when you get rid of them. I do. There is a project to make a universal flyback transformer, I watched a video about it on RUclips. As someone who fixes old arcade games it is really interesting to me. Looking forward to a Coleco Adam video in the future.
The idea of a “universal flyback transformer” is a pipe dream.
The secondary output voltages that feed circuitry other than the CRT anode will vary from model to model. The resonant circuit will vary from model to model.
Sets with larger CRTs usually need higher anode voltages.
If a “universal flyback transformer” was remotely possible, the manufacturers would already be using the exact same flyback transformer across the board - that improves “economies of scale” (saves money so more profitable to do). The flyback manufacturers offered standard catalog models in the hopes that set manufacturers would use those, and they all had several of those standard catalog flyback models.
So don’t hold your breath waiting on one of these.
The TV squealing and shutting down means that the protection circuit is working and cutting down power to avoid more damage.
One strategy to figure out why is usually disconnecting each power rail one by one (disconnecting the diode for example) to see what happens and define on which rail the problem really is. Another possibility is turning off the protection circuit and connect it to a power limiting circuit (serial bulb) to see what gets warm for example, but that is a bit more technical thing to do.
Another easy alternative is you feeding low voltage through an external power supply and check for heating of parts. I guess that is the safest, does not harm the circuits and you would circumvent the protection circuit.
The TV horizontal drive circuit is pretty much a big SMPS with a feedback loop. It tries to start the horizontal drive and if it doesn't see the right voltages on the power rails within a few seconds, it will shut down. There's also a protection circuit that trips if the high voltage becomes too low to prevent the TV from generating X-rays.
@@Stoney3K could be fault in line out or psu stage, i had a sony kv1442 that would go unstable and squealy, it was a 'noisy' zener in the psu,, i have an ancient sony kv1300 that does similar but psu in that seems ok, i havent investigated that one further yet
cracked ferrite core in line transformer or any psu transformer or choke could also cause squealing and shutdown
@@Stoney3K If high voltage becomes too low generates X-rays or the other way round? Conflicting information on the net.
@@s8472-k8i A TV will generate X-rays if the high voltage becomes too high (around 25-30kV for most tubes) because the velocity of the electrons hitting the phosphor is too high.
Something else to check for would be corona discharge. Turn all the lights off to make it as dark as you can and turn the set on with a clear view of the flyback. If it's a insulation issue (HV leak) you may be able to see the blue/purple arc emminating from around the flyback.
While the flyback ring testers are not definitive for testing good, if it says it's bad, it's bad. I'd suggest getting one. They can spot a single shorted turn where your multimeter can't tell. And they're not hard to operate.
There are newly manufactured replacement flybacks, from example by HR Diemen, for this model the replacement would be HR 81731
Adrian's analog attic.
Honestly this channel should be called that 😂
Based on the symptoms, I would guess that either the driver side is weak or some monitoring chip isn't getting the right "it did turn on" signal. Because the outputs all show signs of "getting up there" before it drops down again, I would primarily assume that the flyback is at least almost fine. There might be a high voltage breakdown, yes, but I think the waveform would look slightly different, more like a rising sawtooth than what looked - from afar - like a symmetrical up/down spike... I'd check up on the input drivers next: a.: do the 5V remain stable during power up? Firing that primary coil up takes quite a bit of current; if the main filter caps are weak, maybe the 5V logic voltage has a droop and that causes a reset in the control chip? b.: does the switching transistor "behave"? i.e. is it turning on and off completely and fast enough? Compare base/gate signal to the output towards the primary coil... I had a slightly larger Sony set where the Flyback was knocked clean through the PCB during transport. Tose things are sturdy. Not a huge Sony fan myself, but the TV sets they made were tanks with screens as far as I can tell.
I suspect the driver side is current limiting due to a overload. And I think the safety circuit is doing it's job as the voltages never get where they should be.
How ironic... Back when I was a kid, there were commercials of tv repairmen coming to your house to fix your tv. $39.00 later, they would leave, with a smile on everyone's face... Now, it's hardly an option at all, to have your tv fixed . .. Good thing the videos make money! 👍
I think somebody suggested ringing test for the transformer. That probably related to a Sencore Capacitor-Inductor Analyzer. One of their models was (or is?) LC102. It applies an impulse to a tuned LC combination and counts the number of the decaying ringing waves. It is an indicator of the Q-factor of the inductor. Easy and simple result, without math or any deeper understanding of the L-C-R circuit analysis. However, the (already shown) DER EE instrument DE-5000 can also be used. In this case I would measure the inductance and the Q-factor at 10 kHz, which is closest to the nominal 15.75 kHz use of the horizontal deflection.
Squealing usually signifies a flyback transformer overload. I remember when my father accidentally short-circuited the flyback output, the transformer went squealing like crazy. I even thought it turned into a whistle for a brief moment. When the overload condition was fixed, the transformer started to work as usual. But it look has changed: it became a slightly more brownish color than it was before the overload.
Been there with an early 80s Sony KV2204UB set, about nine months in the LOPT went causing a squegging sound then shutdown. The original LOPT was a UK made part, a Japanese part was installed and saw the set out.
As I remember the Sony sets, they have a lot of protection all arround,so in most cases the sets shuts down.
Well, its seldom that Sony flyback trafo goes bad, but of course this could happend.
Have you checked the safety resistors on the powerrails they sometimes raise in value, also when you start up and power down the unit, there are a poping sound in the speaker, perhaps the main audio amp are shorted from power to output, normally its a differential amp between 2 powerrails.
Keep up the good work
Gotta be honest, this Trinitron would pair perfectly with a PsOne (the slim PlayStation).
I have that set up just like you mentioned and the psone graphics look beautiful on this tv
GOOD SHOW. We are "Chanel Two People" We'll will watch anything that's put's the G in EEKY. You RoCk. Just saying.
try disconnecting all those power lines from the lopt , so nothing is loading it and see if it powers up , also check line driver stage before the line output transistor
Earlier this year, our Bomb Jack cocktail table arcade machine monitor broke. It turns on for a split second, generates high voltage and blows the fuse. Powering it on on a variac, at 40V you could see smoke from the flyback (it's a 100V monitor). Sad. It's one of those unobtainium flybacks, but there's a nutty professor TV serviceman in my country who's working on something that resembles a universal flyback to flyback adapter, read that as "you can put any (similar-ish) flyback in any monitor with this one trick".
Would be cool, that monitor had a bright and vibrant picture despite massive burn-in.
I love you ’Blue steel’ look on the thumbnail.
I’m impressed my iPad Pro speakers played the high frequency sound perfectly. (And my 50+ year old ears could hear it!)
I don't think the flyback is at fault here. Seems to me like the IC that generates the horizontal pulses has a startup mode and a run mode. All the voltages start coming up quickly at the beginning, so the startup seems to work. Maybe the horizontal pulses go bad when the run mode engages after the voltages have come up enough? i would look at the horizontal drive on the scope with a longer timebase to see how it changes over time.
I remember Shango66 having problems with the power supplies on old Sonys. I think they have an unusual feedback loop power supply and problems with cracked flybacks. Just an idea.
At your local garbage dump, in their recycling section maybe someone plopped one off there you can use for parts? Here in PA, they don't care if you drop off electronics and take anything you see (free to drop off and take - lol). I also have a buddy in the business with almost three stories of part TVs, I asked him if he would have one for you.
Hi Dude, that is very interesting. I have the same problems. I would like to continue to repair such devices in the future, so I like to follow such videos.
I had asked a lot of older TV service men if they could help me, but everyone ran away and they said they were glad these tube tvs were over. In fact, it is relatively difficult to repair such tv. For reasons of economy, everything is related together to one thing: flyback transformer, deflection, etc. Well, either everything works or nothing works.
It can very well be that the flyback has an internal short like an insulation failure, that often happens.
I'm not sure it is a good idea to power up the device while the neckboard is disconnected. The ground is interrupted and this is to be avoided. Well the tube is not conducting when not heated, but note that the tube is a capacitor, so theoreticly once a high voltage can come out on the socket pins of the tube ?
Check that the flyback suppression diode hasn't shorted
Just found one of these in ewaste the other day actually. Power cord was cut because of the copper scrapper, but once replaced the set works fine.
I agree most likely the fly back transformer, no obvious shorts, could be worth checking, there's usually a capacitor across the line output transistor, between the collector and emitter, about 7n depending on the screen size, I have had this fail on occasion, but really the sequel noise says it all, a shorted winding inside the tranny, seems a shame to give up because the condition of the set looks pretty good.
Love your work alot fixed a lot of devices due to you, thanks for your wonderful content ;)
Thanks Adrian this fix is well out of my payscale. Cheers
I remember around thirty years ago there was a device you could buy that could test for any shorts inside a fly back transformer, maybe there's a schematic somewhere online, probably some sort of simple oscillator circuit involved, could be worth looking into for future repairs.
@@BlondieHappyGuy Probably the best option, I don't see why it wouldn't be the same, unless the design is radically different to the AC version, I know some older Hitachi sets used the same fly back between the DC and AC only sets, easy to pop off the back and check see if the number matches.
This looks more like one of the secondary load circuits being shorted. If the flyback was bad (shorted) the horizontal output transistor would likely be fried.
@@stevebabiak6997 It does look like there is some sort of loading going on, whether its the transformer or something in the secondary, I was under the impression that a short in the secondary was mostly eliminated,
Although the line output transistor can get damaged, I've found in the past not always, depends how quickly the power supply responds,
Maybe something in the power supply itself, there is usually a cap around 47uf 63v in the primary section, when it goes bad it can throw you off thinking the problem is due to a short, In the end, it's a great help if you can replace and rule out the transformer if things get difficult.
@@electronicarchaeology - using “shotgunning” by changing the flyback isn’t something I’d recommend. They aren’t a regularly stocked component at the typical distributor, and they are expensive to boot. If he can even find one.
I posted a lengthy top level comment giving some ideas. IMO if that flyback is kaput then that set has now become a parts set to cannibalize for the next similar set.
@@stevebabiak6997 You're mistaken there's no shot gunning as you call it involved, if you watch the full video Adrian mentioned that he had another set, A 12v version, if a service engineer suspects the fly back transformer and has another at his disposal, There's nothing wrong in swapping it out even if it for elimination purposes, I've been a service engineer for more than 40 years, my colleagues and I have done this many times.
2:03 THANK YOU YES I heard it thank you for reminding me that my hearing isn't as destroyed as I thought it was! oh wait. it's still there, and it's like 2:58 now. it's permanent. it's worse than I thought.
Oh well, thanks for trying. I just checked to make sure your videos are captioned. If they weren't we'd need to get that set up so I could keep watching your videos!
Haha! I love the "grumpy face" in the thumbnail for this!
Mine turns on and has sound but no picture, any tip or help 😭
The one site that I saw that had this part listed (out of stock) had it for over $70. So probably the best way to do this is to go to an electronics recycler and see if you can get a TV there for parts.
Dude...they don't have be great videos, they have to be Adrian videos...that's why we watch....in this crazy ass world all i can say is, please just keep cranking them out....i hide in my basement and try to repair things too and stream of concsiousness is pretty much the only mental process i use
Yep, exactly. I can relate to this video also, as I have pulled apart things in an effort to repair and never found the cause either.
I had the exact same TV in my kitchen for many years back in the early to late 2000's. It failed in the same manner. I'm into electronics and finally scrapped it. I DID save the picture tube though, it's a pretty advanced tube and I figured someone maybe could use it in the future.
CORRECTED EDITED TEXT:
; Do not work on CRTs unless you know how to be safe!
; ** Today on the bench we have a little SONY TRINITRON
; that has a fault where it squeals and then turns OFF
Your expression on that thumbnail made my day ;-)
That set reminds me of the little Aiwa we had in the kitchen for a bit back in the 90s/00s. Not sure what happened to it.
Seems like a lack of replacement flybacks is what condemns a lot of CRTs to the dump these days.
The side tones kind of makes me suspect there's some resonance fault in either the flyback or the yoke, as both are needed in creating the 15.75kHz resonant tank circuit. It could very well be a magnetic circuit failure (so not an electrical one) in the flyback.
The frequency isn't stable - like it's hunting. But I'm not sure if overloading could do that.
Not every day the thumbnail features a grumpy looking Adrian… my next step would be to locate the shutdown circuit and see if it’s getting activated and start from there.
Would it help to lift some components so to disconnect the flyback from the rest of the circuit and see if voltages run fine (for as long as the TV stays powered)?
Yeah, sometimes I squeal and then shut off, too!
that high pitched whistle? I hear them all the time on Bob Anderson's channel when he fixes vintage tv's the only spare tube tv stuff I have laying around is some parts from an old portable set
Two places you would find a TV like this in the 90's, Yes a Kitchen or a Teenage Girl's Bedroom.
TVs like this have even been featured, in the background of, Movies and TV Shows.
Check the primary side of the flyback transformer and the drive circuit. Disconnect all secondary loads (remove rectifier diodes) and see if anything changes. Could be a bad cap in the primary or secondary.
When doing any troubleshooting, or science in general, only EVER change one variable at a time. Because if you change two or more, and the system starts working, which was the problem? Half splitting is good, but only if you can isolate one half or the other as the fault. I.E. only one variable.
High pitched squealing can indicate a faulty flyback TX. It would certainly be the next component to eliminate if you can get one from somewhere. Wow it doesn't seem that long ago since I was replacing them, but with the dominance of LCD and OLED displays there's not mutch of a demand for them to justify manufacture 😢
I wish a brand out there would make a modern CRT. Imagine the space savings using newer micro technology. Reduce the mainboard by 3/4ths making it 1/4th the size we see here. And add hdmi/dp along side the oldschool connections (rca, coax, component, bnc, etc). With modern tech i bet we could make 240hz crts which would be insane for modern pc gaming
Nice looking little TV - had a quick search on the UK Ebay pages and sadly I don't think we got it over here. Pity as it would make a nice little TV for my one of my retro setups.
Videos where you can't identify the problem can be more useful than fixing the problem. I hope the collective brains trust can help you out.
Test the OpAmp. If I'm not mistaken part of the drive signal goes through it. If it's just part of the audio circuit then it likely has nothing to do with the issue. That's where I'd look though.
I LOVE YOUR CHANNEL!!!
Squeal and shutdown is a fairly good indication of an overloaded power supply, so something on the main bus is likely a short to ground. Hor Output device is a usually a good start. Most Sony's used a Gate Controlled Switch vs a bipolar power transistor for that one. EHT tranny or vert o/p is also possible.
3:09 - "this fault developed while is was actually functional" - lol, isn't that how all faults appear?
Sometimes failures can occur due to poor storage, humidity, etc. I suppose cracks can also happen during transportation. Not *all* faults can come from "normal use", I guess.
The obvious one is glaring.. C515 along with the diode D504 going leaky.. Also the cap C516 in my experience is a source of trouble on these circuits.
Not a common set here in the UK at all.. but there was a good reason I didn't do Sony Trinitrons back in the day..
I do suspect bad caps, even when the caps aren't visibly bad to the human eye.
I had a similar set, black, and the symptoms were also similar. It ended up being the flyback. I managed to get a replacement, but it was 10 years ago. Maybe shango066 can help you with one. He also has a Sony repair video with a strange behavior caused by a flyback.
i do remember one thing about it cuttting off it is because there short somewhere liar in capacity check voltage rails by transfer and see if any voltage drop if yes and there issues in rail to something that shorting it im sure you will find it if you start at beging where power come in and i do believe there just that you over looked it
go back and check it
Try to desolder H-OUT pin of flyback or desolder horizontal out transistor and then try to turn on the set. If it will not squeal, then it's high possibility that flyback is bad.
I took electronics repair as major in high school, but that was half my life ago. My guess would be as you suspect an internal issue in the flyback xformer, or maybe the drive circuit for it?
those schematics need a smart viewer that highlights a line making it wider or in a different color when you click on it.
What a fine looking TV. I wonder why it had a curly power cord?
At 2:15, your spectrum analyzer app showed peaks at 10.5 and 5.25 kHz, which are harmonically related to the expected 15.75 kHz. Maybe why the squeal seemed loud: the ear is much more sensitive at the lower frequencies. But I'm wondering what that tells us about the problem? Maybe the problem is on the primary side, in the horizontal drive circuit?
Oh, it's audible on the video! (at least for those that can hear it normally)
It was a great video!
I didn't know younger Richard Dreyfuss had a RUclips channel.
What's the flyback part number in your other set? Might be close enough to test.
The TDA vertical deflection chips are quite common failures.
I have the same model. It is missing the remote control and could use a cap job.
I deliberately haven't yet watched the video because its asking to guess how this repair went. The facial expression suggests that Adrian is almost annoyed. Given that its a CRT I'm going to guess you stopped it shutting off and then it tried to destroy itself. Its had enough. I have had a few interesting moments with CUB microvitec monitors that have just had enough of life. They fight and bite you like taking the cat to the vets.
I may have missed it but I didn't see the output voltages and wave form of the main PSU output being checked during power on. If the main PSU is failing to maintain the B+ at an adequate voltage under load it could easily cause the flyback to and horizon drive to shut down, and cause the low HT voltages as well. I'm sure you have done this already, just off the video.
Can't you cut the traces on the output side (+/-12 etc) of the flyback to isolate them from the circuit and see what waveforms and voltages you get off the windings?
check the "damper" diode thats across the horz output transistor
Both 12 volt rails and the high voltage are all around 1/3 what they should be but you said you don't get anything on the 180 volt rail. It seems to me the problem is then with the 180 volt line. If disconnecting the neck board gives you confidence the problem is not after the rectification then logically the rectification stage itself could also be the problem. You didn't test that diode on camera and even if the forward drop is okay it might be breaking down under higher reverse voltages. If the diode is bypassed by a capacitor that could also be faulty with voltage.
Spectroid is such a good app
Based on the thumbnail, I figured it would start working for no reason lol
I'm not much up on TV's, but what about the primary to the flyback? You've checked all the secondaries. If dodgy it would effect all the voltages.🥴
If you have working copy of that set, can't you try some part swapping?
Why didn't you try to desolder the +12v and the -12v pins from the transformer to isolate them from the circuit? You could have seen if it was the transformer. OR (I guess) you could have tried to understand where the hissing sound comes from with idk a good microphone? It would have lead you to the problem
Did you rule out that op amp? I'm not saying that with any knowledge, only that you mentioned it on the schematic but didn't mention it again.
Sorry Adrian, fell asleep mid video, but the sound described sounded like a tripler failure. Seeing 1/3rd of the voltage I would expect on the tube .....
Did you say you have another of these TV's you could borrow from?
1/3 = one third so you don't need to add the 'rd' to it. 👍
@@sw6188 Thank you for that. Never too late to learn.
@@connomar55 No worries, not trying to be a smart-ass or anything. You only need 'rd' and 'th' etc when using whole numbers such as 3rd, 5th etc. 👍
Hello I can help you on this repair Put you scope on collector of Hoz out transistor collector and you should see a clean pulse with no hump
If it is clean you have another issue like the la7830 is bad. I have fixed tons of them in the day
Desolder the flyback and test it independently using a test circuit.
you cant usually measure the AC/'pulsing' voltages out of line transformers correctly, measure after any rectifier diode...
I can hear the squeal in the video :P
Do you accept repairs??
I have a Trinitron that needs repair & I cannot find anyone that can do it.
I wonder if there is a Sony crt tv of which we can replace Mac Color Classic screen with..
Would it be possible to find the short with a thermal camera in this case?