Well done CuriousMarc. I'm glad you addressed "Just change the caps" and "Just change the PSU" comments. "Just change the caps" are comments from people with little experience - but they think they know it all. "Just change the PSU" are comments from people who don't restore beautiful equipment to its original state.
"Do it the CuriousMarc way" aka the PROPER way! These days, most techs just seem to swap units, and have no knowledge nor interest in why something fails or how to fix it - everything is seen as a disposable. And those who just recap everything in sight....smh. Excellent stuff as always, Marc. :)
The proper way (and I agree it is the proper way) is just not economical in many cases. Capacitors are cheap (sometimes so cheap the fail) and they are easy to replace. So shotgunning them makes sense in a lot of cases. Also depending on application compared to a resistor they have quite the limited lifetime which is specified in the datasheet as you might know. 80's home computers (Xbox clock battery) are full of leaking (literal) batteries, corroding the circuit-board. For a time period failing caps were the number one cause of failing mainboards and computer power supplies. Then there are the paper-wax caps in tube equipment. They suffer moister ingress. Replace on sight or risk smoke. Replacing them all is not only repair but also preventative maintenance. I do agree that this proper analyses is much more interesting to watch.
Mark's rant was music to my ears. I was taught to find the fault, then find what caused the fault and then fix, commonsense dictates that unless you do how on earth do you know you have really fixed the fault. Back in the seventies I had a job fixing out of spec switching supplies that came off a production line. Youngsters now probably wouldn't believe that such a thing happened but manufacturing and components were then very expensive. Steve
Bart Zuidgeest Those mass capacitor failures were industrial espionage gone wrong. There was nothing wrong with the source formulation - except the thieves didn’t steal all of it. And all the companies that then perused that stolen formulation have just shot themselves in the foot. There was nothing wrong inherently with the capacitors. They were manufactured in a way that gave them an Eingebautes Verschluss - a predefined end-of-life. There was nothing random nor unexpected here - except we the customers initially didn’t know what was up. Everyone in the know in the industry knew exactly what was up. And it had zilch to do with capacitors per se. the capacitors were basically rigged to fail.
@@absurdengineering The cause hardly matters, fact is that many classes of electronics contain failing capacitors necessitating replacement. You can leave the "good" ones in, but that is just asking for having to revisit a device in the future. Also neither the rifa X cap or paper wax type (in tube equipment) example have anything to do with espionage. Shotgunning might just be the most economical in time spend on a device, even if it is not a "proper" repair
There is a bit of that. But check for the price of this unit on eBay or a used test equipment site. You'll quickly understand why I spent so much time on it!
@@CuriousMarc we are very much the beneficiaries of the adventure regardless of the "business case" or economics of it, and as such quite grateful you've made us a part of it. Merci beaucoup.
there is no easy way to replace this PSU (as explained in the previous video). By this: Repairing it is the only path to go. I am still unable to tell why they used this double regulator approach before coming to the main DC rails. making universal voltage input easier in the age before fast/effective Mosfets became available? (having helper-rails coming from linear regulators is normal in that era, so i don not count that.)
Yeah I just fixed a cassette deck (Panasonic 612) I found in the e-waste. The circuit board was smashed (in pieces), components were missing or broken, but I still managed to fix it. 200 euros in labour (and 30 cents in parts). Worth it? No way! (30 euros on eBay) Fun? Hell Yeah!
LOL - that's the first time I've seen the output of a scope being taken into an other scope for being good front-end. But you're perfectly right. I would have had never remembered of the Y-output, maybe because I don't know any modern scope even having such an output. Very well done! (to both of you, Marc *and* Tektronix for it's brilliant high-end scope!) Hats off!
Love it! I’ve never really had the guts to troubleshoot switchmodes but you’ve spurred my interest enough as well as showing an excellent view of how to logically and methodically go about it. Brilliant videos Marc - can’t wait for the next one!
Beautiful stuff.Its not about the time it may take,or the amount of hair that you may lose in the process,its all about what you learn along the way, you NEVER forget it.It is priceless!!! I was an engineer for about 20 years fixing equipment in the medical industry,and for broadcasting stations such as BBC ,and ITN in the UK,as well as broadcasters abroad. I loved that part of my working life,cant do it anymore, but i remember a lot of my radio and electronics theory,i self taught to fault find and understand microprocessors,and had a ball setting up logic analysers for pretty hairy work with the first multitasking processor from intel. A lot of that knowledge is intact. Ive been closely following the amazing Marc,and the terrific Shariar at the Signal Path. I have a good understanding of what they're doing,because of my previous investment in time,effort,and hair loss!! Marc,,,,rant away, you're absolutely right mate.. I thoroughly enjoy your channel(except the electromechanical teleypes ugh!!). Keep it up,and thank you so much. PS the atomic clock project and explanation was a beauty. I studied (well partly,long story) a physics undergrad degree here in London,i did think atomic clocks were exploiting orbital energy levels,not the spins,you taught me something new Marc. Ignore the naysayers!! Please keep it up..
I love this channel. Diagnosing the exact fault like this is way more satisfying than replacing the whole thing or mass-replacing parts, and showing the process here is creates an excellent resource to learn from :)
The guy over at South Main Auto refers to mindless parts swapping as "firing the parts cannon". The true problem must be found before anything is replaced. You have my respect Marc, I never like working on switchers.
And this is exactly why I like your channel so much. Excellent video Marc! Very addictive and informative, learning a lot too! Thanks for doing these projects!
The fun of it is definitely figuring everything out. Makes it more satisfying when it finally works too! Also I've gotta appreciate the HP-15C(?) in a couple shots.. Love that series, wish they weren't unobtainium lol
I used to fix this sort of thing for a living, and my only comment is.. don't poke your fingers in the HT side, unless you have plastic fingers. This applies equally when switched off and unplugged as it does when it is plugged in. That 300V DC gets a little bit exciting if it hasn't discharged. Things get even more exciting when you start playing with real HT (CRT drive circuits and so forth). Wear a suitable rubber glove and/or keep your left hand in your pocket at all times. Isolation transformers and RCD breakers will only provide very basic protection, and fuses are only there to ensure the building doesn't burn down. The best protection is the lump of porridge between your ears. Always assume you are going to get a belt, at least that way when you do, its less of a surprise.
The master of suspense!!! I'm getting that AGC 'can't wait for the next episode' feeling. Actually thinking back in time used to be able to get rebuild kits for shot gunning SMPS on some products. One duff part in the chain takes everything else out before you can even contemplate what happened.... All very costly and time consuming. Also those very much manufacturer specified devices that you must use or it just goes bang again down the road....
My experience with the MOSFET driver ICs is that they won't tolerate the Vss droping below the input side Vee by more than a fraction of a volt; the failure mode is often to turn both MOSFETS on causing shoot through. Obviously that doesn't apply to devices like the ICP2104 where the supplies both refer to the COM pin, but older devices like the IR2110 suffer this weakness.
I take both approaches. It has been wonderful spending some time on an old Everexx server that I have here, and painstakingly going through it part by part and figuring out its stability issues without just indiscriminately swapping parts. Much of its control board is made up of pal's that can't be replaced. I also take the same approach to audio equipment which I care about, as their are too many variables which can quickly become a money sink if you don't take the time to investigate. On the other hand things like my Mac LCII and LCIII immediatly got all caps replaced before any sort of troubleshooting even began. As they were both known to work before being put away and one still lights up with errors and the other has no life at all. And 99% of the time that solves the problems. And is something which needs to eventually be done to preserve them.
OMG! 8:24 the HP15C RPN calculator!!! ;-) My first set of batteries took me through engineering school, through my masters, and ten years of work. The second set is still going strong, replaced sometime in the late 90s.
LOL! It came out in my junior year at Pitt.. and I was in electromagnetics II. I was the only one that could do all of the polar/rect, rect/polar conversions and crushed the tests.
This is turning into the 'AGC' the sequel love it. its far to easy to part swap, module swap complete unit swap. you learn absolutely bugger doing it that way. Also its quiet easy to fault find and fix when you have full service diagrams and schematics. Its a totally different story when you have neither and Only real skilled folks can achieve success. If folks would actual listen to what mark has said in the videos he has all ready checked the usual suspect capacitors. Im really enjoying these episodes during lock down and extremely jealous of marks huge collection of very very desirable diagnostics gear its hardware porn for the electronics nerd
Nice work, well see if Murphy tosses you another curve ball. Post repair RCA is going to be interesting. My bet was someone shorted the output or a cap went bad post DC-DC converter which took out the FET which took out the driver. The last person replaced the cap but by then it was too late, the damage had been done further up the chain.
The best way is to debug and repair...if we want to learn something , but done by you is a magic 🧠🧐💡. The way your PS failed make me suspect of an overload in the secondary side of it. A shorted rectifier diode as well as capacitors are good candidates. I’m “Curios” to see how it will goes😬.
Marc! You have a *very impressive* collection of test equipment! I had a tek 7904 for several years, (and a bunch of plug-ins) however, it had a list of several faults which included the character generator, and the +/- 15 volt rail. I fixed the PS, but could never figure out the CG fault... After it collecting dust for several years, I finally sold it at a HAMFEST for a third of what I paid for it... :(
I think when an IC like that fails, there likely is another external reason for it (so the next one will fail again). Either its supply voltage is incorrect, its input signal is above its supply signal, or it gets a high voltage back from the failed MOSFET gate.
You have a point, I have seen many failed MOSFETS that short to the gate, and damage whatever drives them. And the failed FET can be for many reasons.. maybe the magnetics design was poor and the BH field walks from center, saturates, and pops one FET..
It does, but by then the drain of the kickstart MOSFET is held at 12V by the takeover supply. The kickstarter pulses are 15V. And the turn on voltage of the MOSFET is 4V. So the MOSFET will feel only 3V on its gate during the pulse and won't turn on once the takeover supply takes over. Took me a long while to figure this one out! They say the thermistor is for protection, I think if the kickstart MOSFET were to fail in the "on" position or was on for too long. This whole thing smells like their control circuits were drawing too much power, so they went to this elaborate scheme to still make it work with a temporary supply drawn from a resistor on the 300V, but that would only work for a very short amount before the whole thing over heated. So they built a more powerful take over supply which is fed by an extra low voltage winding from the *primary* of the DC-DC. This is all quite unusual.
@@CuriousMarc I think your diagnosis is right. The supply is pulsed to give the resistor less dissipation. Usually it would just use the simple schematic you have drawn first. However, there are plenty unusal things in this supply... at least when compared to today's designs. The use of a separate buck converter then DC-DC converter can be a good idea but you would want it to "ride the sinewave", i.e. much smaller storage caps after the main rectifier, and then some storage caps after the buck converter. This is commonly used today for "power factor correction", i.e. to prevent the problem that the supply only takes current at the mains sinewave peaks and thus causes harmonic distortion of the mains. (this PFC is different from "cosine-Phi correction" as used with mainly inductive loads)
Just wondering what is the wattage on the MOSFET transistors if less then 15W what about using VN66AF MOSFET transistors which are designed for 15W dissappation.
Curiousmarc, what does various switching power supply all have a different start up sequence circuit? to view the start up sequence circuit on an oscilloscope you used the external trigger input?
Recapping is the new trend on RUclips. Something not working? Replace the caps. These kinds of comments annoy me, really. Replacing the capacitors only works in some modes of failure, where the power from the supply is unstable. And even in that circumstance, the capacitors may not be the components to blame. Once I've fixed a Mean Well RS-15-12 power supply. The whole control chain blew up, along with the fuse on the primary side. So I've replaced the opto-coupler, that no longer worked, along with the controller chip (with integrated MOSFET) that had its top blown off, and also some other components. The caps were all fine and no recap was done. The repaired supply still works to this day.
Good to see 50 year old technology (7A22 differential amp) come to the rescue when the more modern devices aren't up to the job. Maybe this is a bit of a boost for us old-timers, showing that younger and newer is not necessarily better.
These Tek scopes were royalty back then. Not quite 50 years old, more like 30 years old. They used to cost a fortune, but oh so awesome. Then you can get a specialized drawer for measuring almost anything! A collector's dream, the drawers are quite affordable now.
@@CuriousMarc The 7A22 was introduced in 1970 so is now 50 years old. Some of the internal design was derived from earlier Tek products so is probably more than 60 years old. The 7854 was introduced in 1980 so it is a relatively young 40 years. You are right about the 7000 series now being very affordable compared to its astronomical original pricing but they are not just collector's items as they are still useful instruments. I occasionally roll out one of my 7000 mainframes and select the appropriate plug-in whenever I have a difficult measurement problem that can't be easily done with a modern scope.
Devices like an IR2106 or 2150, even FAN7380s suffer over extended periods of time from thermal issues. What happens revolves around the Q on the gate not I'ing fast enough leading to increased rise or fall times. The downside of this is a tiny overlap during switching is, Eventually peak currents do damage to the coulomb barrier within one of the MOSEFTS, leading to a angry pixie riot taking place in the die. Most people head for caps in smps and while this is partly true due to constant thrashing at high frequencies, sometimes its just a good old lazy gate somwhere
Interesting. However at the end 14:45 you should first mechanically tighten the MOS-FET screw and then only solder the pins. Otherwise you get permanent stress on the said pins.
First the Sparkenmaschine - now this Sparken-PSU. I have a feeling the upcoming video is a collaboration with ElectroBoom (or at least following his general concept of combining hard facts with special effects)... ;-)
this is really a a hell of a PSU. there is probably quite an evolution behind such a design. Because "out of the blue" (hopefully) nobody comes up with such a contraption.
This is so awesome. Of course anyone can shoot parts at it but you won't know exactly what went wrong, and worse, you'll never fully understand what's going on.
I would highly recommend a thermaltronics soldering iron. It is just like a metcal much less expensive (at least when I bought mine) The iron you have makes me cringe. No I am not affiliated with them, I just like their irons better than I like Metcal, Weber, or Hakko. YMMV. Big applause for your episode - it's nice to see an actual engineer at work and not just somebody who blindly shotguns everything.
But I love my Weller! Heats up incredibly fast, very precise temp control, many interchangeable tips I can (could) get from Fry’s, and super sturdy. I’ll take a look at your recommendation though.
@@CuriousMarc Hehe, I'm still using my Weller WP-25, acquired in 1971, and my other WP-25 bought in 1978. I collected a large stock of the range of tips from DIgikey in the 90's when I had some extra money. Plug them in, wait 5 minutes and start soldering.
Damn that scope acquisition mode and playback is one really fancy feature that probably is too deep in the thick scope manual to really get use of :) You need to be reasonable scope wizard already to start being interested in that advanced features. The modern scopes are way too complex :)
@@CuriousMarc That is actually pretty normal. I have experience with R&S RTM3004 which base price is about 3k€ but with options can go all the way up to 15k€ and worse all the capability is already physically in that base model but you pay to unlock them..
Switchmode powersupplys are sooo complicated q.q i have 3 that i can't repair because i don't know what's exactly wrong with them.... Tow of them have a deat starting circuit but maybe i can fix them now with your knowledge thank you :)
They are not so complicated, but they very often suffer from the problem that they cannot work unless everything is working OK and when one part fails it is difficult to do measurements because the entire thing is just dead. Also, one failing part may destroy other parts, and the generic way of solving problems (check if parts have failed an replace them) is not very successful on those supplies because usually you will first replace the parts that got blown by other failures, so the replacements will just fail again.
@@Rob2 Well said! You need soft start and shutdown to ensure that energy stored in inductance can safely run out. In a failure a sudden change in current causes high voltages according to V = L x dI/dt blowing up every semiconductor in sight! There are however testing tricks that can help: Use a Variac and try to run the thing @ reduced input voltage. Override the control circuit with a signal generator to see if the power chain is intact (running in open loop). Last test the circuit @ full voltage and load with control loop closed while hiding under the desk :)
I’ve had some luck with substituting 9V batteries (sometimes 2 in series) for various “standby” voltages within switchers. The fates were kind and when invariably one of such kludges would get 300VDC across the terminals, it didn’t cause any major nor even minor body damage. I did run a power supply in my fridge with a slightly flat 9V battery in place of a 12V Zener that had failed. Overnight I found a replacement part, and the battery got a bit of trickle charge to recover :)
@CuriousMarc, have you recorded anywhere, on video or on "paper" your background in being interested in electronics? like maybe from when you were young?
I would not call that a rant, more an explanation why you do it the way you do it and also as an advise why this would be the better way (learning, saving parts, sometimes something that can not be swapped, etc).
I agree mostly with the "rant" What you do is the proper way (certainly for this situation), but it is just not economical in many cases. Capacitors are cheap (sometimes so cheap they fail premature) and they are easy to replace. So shotgunning them makes economic sense in a lot of cases. Also depending on application compared to a resistor they have quite the limited lifetime which is specified in the datasheet as you must know. 80's home computers (classic macs, Xbox clock battery) are full of leaking (literal) batteries, corroding the circuit-board. For a time period failing caps were the number one cause of failing main boards and computer power supplies. Then there are the paper-wax caps in tube equipment. They suffer moister ingress. Replace on sight or risk smoke. A few might be fine, but do you really want to keep returning to the same job over and over? Often I consider replacing them all not so much repair but also preventative maintenance. I do agree that this proper analyses is much more interesting to watch. O and before I forget the example of the Rifa safety caps. Yellow transparent housing, very specific series. They swell up crack the housing and then blow up. I found good ones, but never left one in. Quite sure the customer rather not come back twice....
Wer misst, misst Mist. (German engineer's saying. Means "He (or she) who measures, is measuring crap") Which basically means "Know the limits (and quirks) of your measuring gear and keep in mind it can affect the circuit you're measuring" (I'm kinda disappointed I can't give this video more than one thumb up)
Absolutely, you can do that too. That’s what most people would do actually. But that's not nearly as powerful as using a differential probe, where you can probe absolutely anywhere, completely off the ground, the two sections at the same time if you wish. Unfortunately I ran out of common mode margin. I got the x100 attachment since then....
CuriousMarc It’s probably good that there was no hard protection against exceeding common mode limits. I’ve had the dubious pleasure of using a probe that had some unforgiving fast-acting semiconductor clamps that protected the input stages from common mode overvoltage. The clamps were totally up to their task. The fault current they shunted was sufficient to vaporize the tips of the probe. Other than that, the probe survived unscathed. My corneas were not that happy though - whether it was the UV or the rapidly condensing metal vapor sent their way. Live and learn - and it helped that I was only about 20 at the time.
Why didn’t you replace the electrolytic caps 😂😂😂😂 because the damn thing Is detonating mosfets 😯 maybe your should just replace the power supply 🤬🤬🤬🤬🤬🤬 it’s got 6000 rails and two that are variable!!! 😳 what kind of TV did you say this was out of ???? ☢️ 🍄 ☁️
Three idiots do not know what is a nice video... Probably preferring car crashes or motor explosion compilations... Keep going Marc! I know what it means to understand how these things are working and how to repair them. As you say, the world will always be divided in two categories : people who think that repairing is just replacing a part or a complete device. And the others...
I think this is more of gaining an understanding of whats failing and causing the problem. Hopefully when you find it that's much more rewarding than shot gunning the whole board. Maybe in a fast turnaround customer is paying situation then that can be an effective approach as would be just replace the board. The cost / availability of board like this though, not first choice.
I am not sure who is first, seems like @Wilian Henrique Rosada clicked faster. But there is plenty of broken vintage bits to distribute from this supply. How about you get a free vintage kickstart pulse!
![Noob To Max With DRAGON REWORK In Blox Fruits [FULL MOVIE]](http://i.ytimg.com/vi/LnBMOinoOvA/mqdefault.jpg)
Well done CuriousMarc. I'm glad you addressed "Just change the caps" and "Just change the PSU" comments.
"Just change the caps" are comments from people with little experience - but they think they know it all.
"Just change the PSU" are comments from people who don't restore beautiful equipment to its original state.
"Do it the CuriousMarc way" aka the PROPER way! These days, most techs just seem to swap units, and have no knowledge nor interest in why something fails or how to fix it - everything is seen as a disposable. And those who just recap everything in sight....smh. Excellent stuff as always, Marc. :)
This is the difference between a technician and an engineer. A technician knows what. An engineer knows how and why - and has the skills to find out.
The proper way (and I agree it is the proper way) is just not economical in many cases. Capacitors are cheap (sometimes so cheap the fail) and they are easy to replace. So shotgunning them makes sense in a lot of cases. Also depending on application compared to a resistor they have quite the limited lifetime which is specified in the datasheet as you might know. 80's home computers (Xbox clock battery) are full of leaking (literal) batteries, corroding the circuit-board. For a time period failing caps were the number one cause of failing mainboards and computer power supplies. Then there are the paper-wax caps in tube equipment. They suffer moister ingress. Replace on sight or risk smoke. Replacing them all is not only repair but also preventative maintenance. I do agree that this proper analyses is much more interesting to watch.
Mark's rant was music to my ears. I was taught to find the fault, then find what caused the fault and then fix, commonsense dictates that unless you do how on earth do you know you have really fixed the fault. Back in the seventies I had a job fixing out of spec switching supplies that came off a production line. Youngsters now probably wouldn't believe that such a thing happened but manufacturing and components were then very expensive.
Steve
Bart Zuidgeest Those mass capacitor failures were industrial espionage gone wrong. There was nothing wrong with the source formulation - except the thieves didn’t steal all of it. And all the companies that then perused that stolen formulation have just shot themselves in the foot. There was nothing wrong inherently with the capacitors. They were manufactured in a way that gave them an Eingebautes Verschluss - a predefined end-of-life. There was nothing random nor unexpected here - except we the customers initially didn’t know what was up. Everyone in the know in the industry knew exactly what was up. And it had zilch to do with capacitors per se. the capacitors were basically rigged to fail.
@@absurdengineering The cause hardly matters, fact is that many classes of electronics contain failing capacitors necessitating replacement. You can leave the "good" ones in, but that is just asking for having to revisit a device in the future. Also neither the rifa X cap or paper wax type (in tube equipment) example have anything to do with espionage. Shotgunning might just be the most economical in time spend on a device, even if it is not a "proper" repair
Engineer: A person who will spend $40 and 16 hours to fix a $15 remote control.... LOL! Keep banging on it Marc!
There is a bit of that. But check for the price of this unit on eBay or a used test equipment site. You'll quickly understand why I spent so much time on it!
@@CuriousMarc we are very much the beneficiaries of the adventure regardless of the "business case" or economics of it, and as such quite grateful you've made us a part of it. Merci beaucoup.
there is no easy way to replace this PSU (as explained in the previous video). By this: Repairing it is the only path to go.
I am still unable to tell why they used this double regulator approach before coming to the main DC rails. making universal voltage input easier in the age before fast/effective Mosfets became available?
(having helper-rails coming from linear regulators is normal in that era, so i don not count that.)
Yeah I just fixed a cassette deck (Panasonic 612) I found in the e-waste. The circuit board was smashed (in pieces), components were missing or broken, but I still managed to fix it. 200 euros in labour (and 30 cents in parts). Worth it? No way! (30 euros on eBay) Fun? Hell Yeah!
@@senilyDeluxe 200 euros investment in yourself !
LOL - that's the first time I've seen the output of a scope being taken into an other scope for being good front-end. But you're perfectly right. I would have had never remembered of the Y-output, maybe because I don't know any modern scope even having such an output. Very well done! (to both of you, Marc *and* Tektronix for it's brilliant high-end scope!)
Hats off!
It is not about the saving money. It is about process of curiosity. I loved it.
Love the opening rant! I so agree with you. Fix the original problem, not try and compensate for it.
Love it! I’ve never really had the guts to troubleshoot switchmodes but you’ve spurred my interest enough as well as showing an excellent view of how to logically and methodically go about it. Brilliant videos Marc - can’t wait for the next one!
Beautiful stuff.Its not about the time it may take,or the amount of hair that you may lose in the process,its all about what you learn along the way, you NEVER forget it.It is priceless!!!
I was an engineer for about 20 years fixing equipment in the medical industry,and for broadcasting stations such as BBC ,and ITN in the UK,as well as broadcasters abroad.
I loved that part of my working life,cant do it anymore, but i remember a lot of my radio and electronics theory,i self taught to fault find and understand microprocessors,and had a ball setting up logic analysers for pretty hairy work with the first multitasking processor from intel.
A lot of that knowledge is intact.
Ive been closely following the amazing Marc,and the terrific Shariar at the Signal Path.
I have a good understanding of what they're doing,because of my previous investment in time,effort,and hair loss!!
Marc,,,,rant away, you're absolutely right mate..
I thoroughly enjoy your channel(except the electromechanical teleypes ugh!!).
Keep it up,and thank you so much.
PS the atomic clock project and explanation was a beauty.
I studied (well partly,long story) a physics undergrad degree here in London,i did think atomic clocks were exploiting orbital energy levels,not the spins,you taught me something new Marc. Ignore the naysayers!!
Please keep it up..
Best channel on RUclips. I tried to explain EBCDIC and ASCII to a student this week and I was thinking of your crew the whole time! Long live chad!
I love this channel. Diagnosing the exact fault like this is way more satisfying than replacing the whole thing or mass-replacing parts, and showing the process here is creates an excellent resource to learn from :)
The guy over at South Main Auto refers to mindless parts swapping as "firing the parts cannon". The true problem must be found before anything is replaced. You have my respect Marc, I never like working on switchers.
Always place socket when replacing a ic. Makes I easier when more goes wrong.
Nice to see you didn’t give up on this repair :)
...and that's why this channel name is " Curious Marc"...
Indeed.
WHY would an Engineer go to such great lengths designing such a monster, KISS !!!! Cant wait to watch the outcome, TNX 4 another great video !!!
Thank you for documenting your troubleshooting, Marc! Helpful even for other professionals. :)
And this is exactly why I like your channel so much. Excellent video Marc! Very addictive and informative, learning a lot too! Thanks for doing these projects!
This is proper electronic debuggering
The fun of it is definitely figuring everything out. Makes it more satisfying when it finally works too!
Also I've gotta appreciate the HP-15C(?) in a couple shots.. Love that series, wish they weren't unobtainium lol
The suspense. You (and that PSU) have a great sense for dramaturgy.
Dramaturgy...new word.
I used to fix this sort of thing for a living, and my only comment is.. don't poke your fingers in the HT side, unless you have plastic fingers.
This applies equally when switched off and unplugged as it does when it is plugged in. That 300V DC gets a little bit exciting if it hasn't discharged. Things get even more exciting when you start playing with real HT (CRT drive circuits and so forth). Wear a suitable rubber glove and/or keep your left hand in your pocket at all times. Isolation transformers and RCD breakers will only provide very basic protection, and fuses are only there to ensure the building doesn't burn down. The best protection is the lump of porridge between your ears. Always assume you are going to get a belt, at least that way when you do, its less of a surprise.
The master of suspense!!! I'm getting that AGC 'can't wait for the next episode' feeling.
Actually thinking back in time used to be able to get rebuild kits for shot gunning SMPS on some products.
One duff part in the chain takes everything else out before you can even contemplate what happened.... All very costly and time consuming. Also those very much manufacturer specified devices that you must use or it just goes bang again down the road....
My experience with the MOSFET driver ICs is that they won't tolerate the Vss droping below the input side Vee by more than a fraction of a volt; the failure mode is often to turn both MOSFETS on causing shoot through. Obviously that doesn't apply to devices like the ICP2104 where the supplies both refer to the COM pin, but older devices like the IR2110 suffer this weakness.
I take both approaches. It has been wonderful spending some time on an old Everexx server that I have here, and painstakingly going through it part by part and figuring out its stability issues without just indiscriminately swapping parts. Much of its control board is made up of pal's that can't be replaced. I also take the same approach to audio equipment which I care about, as their are too many variables which can quickly become a money sink if you don't take the time to investigate.
On the other hand things like my Mac LCII and LCIII immediatly got all caps replaced before any sort of troubleshooting even began. As they were both known to work before being put away and one still lights up with errors and the other has no life at all. And 99% of the time that solves the problems. And is something which needs to eventually be done to preserve them.
OMG! 8:24 the HP15C RPN calculator!!! ;-) My first set of batteries took me through engineering school, through my masters, and ten years of work. The second set is still going strong, replaced sometime in the late 90s.
LOL! It came out in my junior year at Pitt.. and I was in electromagnetics II. I was the only one that could do all of the polar/rect, rect/polar conversions and crushed the tests.
First thing I bought was a isolation transformer. Safer and no need for a differential probe. Used a inverter a couple weeks too as a replacement.
This is turning into the 'AGC' the sequel love it. its far to easy to part swap, module swap complete unit swap. you learn absolutely bugger doing it that way. Also its quiet easy to fault find and fix when you have full service diagrams and schematics. Its a totally different story when you have neither and Only real skilled folks can achieve success. If folks would actual listen to what mark has said in the videos he has all ready checked the usual suspect capacitors. Im really enjoying these episodes during lock down and extremely jealous of marks huge collection of very very desirable diagnostics gear its hardware porn for the electronics nerd
Makes me think of that saying: 'Tighten one bolt, two more comes loose.'
In the software world, fix one bug and create a hundred more
[begin rant... end rant] good rant 👍
The joys of repairing a switch mode power supply. I feel the pain.
Nice work, well see if Murphy tosses you another curve ball. Post repair RCA is going to be interesting. My bet was someone shorted the output or a cap went bad post DC-DC converter which took out the FET which took out the driver. The last person replaced the cap but by then it was too late, the damage had been done further up the chain.
Argh! The suspense is killing me! Lolol, Love the videos ! Thanks!
The best way is to debug and repair...if we want to learn something , but done by you is a magic 🧠🧐💡. The way your PS failed make me suspect of an overload in the secondary side of it. A shorted rectifier diode as well as capacitors are good candidates. I’m “Curios” to see how it will goes😬.
Marc! You have a *very impressive* collection of test equipment!
I had a tek 7904 for several years, (and a bunch of plug-ins) however, it had a list of several faults which
included the character generator, and the +/- 15 volt rail. I fixed the PS, but could never figure out the CG fault...
After it collecting dust for several years, I finally sold it at a HAMFEST for a third of what I paid for it... :(
I agree with not replacing all the caps, but you have some tantalums in there. They are notorious for shorting, and are easy to test.
Merci Marc tes vidéos sont au top, on apprend beaucoup de choses! J'ai hâte de voir la suite.
this is an awesome set of videos thank you!!
I think when an IC like that fails, there likely is another external reason for it (so the next one will fail again).
Either its supply voltage is incorrect, its input signal is above its supply signal, or it gets a high voltage back from the failed MOSFET gate.
You have a point, I have seen many failed MOSFETS that short to the gate, and damage whatever drives them. And the failed FET can be for many reasons.. maybe the magnetics design was poor and the BH field walks from center, saturates, and pops one FET..
4:24 So the KickStarter pulses even when it is not needed? What this termistore is for?
It does, but by then the drain of the kickstart MOSFET is held at 12V by the takeover supply. The kickstarter pulses are 15V. And the turn on voltage of the MOSFET is 4V. So the MOSFET will feel only 3V on its gate during the pulse and won't turn on once the takeover supply takes over. Took me a long while to figure this one out! They say the thermistor is for protection, I think if the kickstart MOSFET were to fail in the "on" position or was on for too long. This whole thing smells like their control circuits were drawing too much power, so they went to this elaborate scheme to still make it work with a temporary supply drawn from a resistor on the 300V, but that would only work for a very short amount before the whole thing over heated. So they built a more powerful take over supply which is fed by an extra low voltage winding from the *primary* of the DC-DC. This is all quite unusual.
@@CuriousMarc I think your diagnosis is right. The supply is pulsed to give the resistor less dissipation. Usually it would just use the simple schematic you have drawn first.
However, there are plenty unusal things in this supply... at least when compared to today's designs.
The use of a separate buck converter then DC-DC converter can be a good idea but you would want it to "ride the sinewave", i.e. much smaller storage caps after the main rectifier, and then some storage caps after the buck converter.
This is commonly used today for "power factor correction", i.e. to prevent the problem that the supply only takes current at the mains sinewave peaks and thus causes harmonic distortion of the mains.
(this PFC is different from "cosine-Phi correction" as used with mainly inductive loads)
Love the CuriousMarc way
man your oldie is beautiful
Such informative video’s. Really addictive!
AC / DC => Thunderstruck and almost happened ;) Cheers from Belgium Marc
I really enjoy watching your content.
Glad to see a 7854 make an appearance!
love that scope!
Just wondering what is the wattage on the MOSFET transistors if less then 15W what about using VN66AF MOSFET transistors which are designed for 15W dissappation.
Can't wait to see the teased destructive auto-diagnostic feature of this PSU \o/
Curiousmarc, what does various switching power supply all have a different start up sequence circuit? to view the start up sequence circuit on an oscilloscope you used the external trigger input?
Recapping is the new trend on RUclips. Something not working? Replace the caps. These kinds of comments annoy me, really. Replacing the capacitors only works in some modes of failure, where the power from the supply is unstable. And even in that circumstance, the capacitors may not be the components to blame.
Once I've fixed a Mean Well RS-15-12 power supply. The whole control chain blew up, along with the fuse on the primary side. So I've replaced the opto-coupler, that no longer worked, along with the controller chip (with integrated MOSFET) that had its top blown off, and also some other components. The caps were all fine and no recap was done. The repaired supply still works to this day.
Curious Marc? more like spurious spark! ;)
Very nice video :D. keep doing video like this one.
Good to see 50 year old technology (7A22 differential amp) come to the rescue when the more modern devices aren't up to the job.
Maybe this is a bit of a boost for us old-timers, showing that younger and newer is not necessarily better.
These Tek scopes were royalty back then. Not quite 50 years old, more like 30 years old. They used to cost a fortune, but oh so awesome. Then you can get a specialized drawer for measuring almost anything! A collector's dream, the drawers are quite affordable now.
@@CuriousMarc The 7A22 was introduced in 1970 so is now 50 years old. Some of the internal design was derived from earlier Tek products so is probably more than 60 years old. The 7854 was introduced in 1980 so it is a relatively young 40 years.
You are right about the 7000 series now being very affordable compared to its astronomical original pricing but they are not just collector's items as they are still useful instruments. I occasionally roll out one of my 7000 mainframes and select the appropriate plug-in whenever I have a difficult measurement problem that can't be easily done with a modern scope.
@@stephenbell9257 Wow I did not know they were that old. Even more impressive! Thanks for the info!
Time for Switcher Nightmare T-shirt!
Great video. I'm learning a lot. Thanks.
Devices like an IR2106 or 2150, even FAN7380s suffer over extended periods of time from thermal issues. What happens revolves around the Q on the gate not I'ing fast enough leading to increased rise or fall times. The downside of this is a tiny overlap during switching is, Eventually peak currents do damage to the coulomb barrier within one of the MOSEFTS, leading to a angry pixie riot taking place in the die.
Most people head for caps in smps and while this is partly true due to constant thrashing at high frequencies, sometimes its just a good old lazy gate somwhere
For the love of electrons, stop with the cliffhangers!
You’re killing me Marc! 😜
Interesting.
However at the end 14:45 you should first mechanically tighten the MOS-FET screw and then only solder the pins. Otherwise you get permanent stress on the said pins.
In AC/DC impulse power supply PWM controller working on feedback, if output voltage doesn't fit the PWM IC cut off power and trying start again.
First the Sparkenmaschine - now this Sparken-PSU. I have a feeling the upcoming video is a collaboration with ElectroBoom (or at least following his general concept of combining hard facts with special effects)... ;-)
Boy, was I right... 😂😂😂
this is really a a hell of a PSU. there is probably quite an evolution behind such a design. Because "out of the blue" (hopefully) nobody comes up with such a contraption.
Can’t wait!
If my osciloscope not grounded and i use 10x probe is it neccessary to use differencial probe???
As long as your scope is not grounded you should be fine with 10x probes.
@@CuriousMarc thanks alot
why not solder regular 60w light bulb instead of a fuse. It will not affect unloaded PSU but in case of overload it will save mosfets.
A bulb might not be fast enough to save the Mosfets. A quick fuse might.
@@Citronitroify a bulb will limit the current.
This is so awesome. Of course anyone can shoot parts at it but you won't know exactly what went wrong, and worse, you'll never fully understand what's going on.
I still think you need to work backwards to verify the sub supplies are ok, and check the feedback circuitry.
Ohhh ends with a cliff hanger. looking forward to next.
Love the education...thank you
I hope you at least went over the tantalums with an ohm meter to check for obvious shorts.
Who hasn't spent hours trying to diagnose a bad measurement? People who replace caps and power supplies, that's who.
I would highly recommend a thermaltronics soldering iron. It is just like a metcal much less expensive (at least when I bought mine) The iron you have makes me cringe. No I am not affiliated with them, I just like their irons better than I like Metcal, Weber, or Hakko. YMMV. Big applause for your episode - it's nice to see an actual engineer at work and not just somebody who blindly shotguns everything.
But I love my Weller! Heats up incredibly fast, very precise temp control, many interchangeable tips I can (could) get from Fry’s, and super sturdy. I’ll take a look at your recommendation though.
@@CuriousMarc Hehe, I'm still using my Weller WP-25, acquired in 1971, and my other WP-25 bought in 1978. I collected a large stock of the range of tips from DIgikey in the 90's when I had some extra money. Plug them in, wait 5 minutes and start soldering.
Damn that scope acquisition mode and playback is one really fancy feature that probably is too deep in the thick scope manual to really get use of :) You need to be reasonable scope wizard already to start being interested in that advanced features. The modern scopes are way too complex :)
It’s worse than that. Keysight makes you pay for that added feature...
@@CuriousMarc That is actually pretty normal. I have experience with R&S RTM3004 which base price is about 3k€ but with options can go all the way up to 15k€ and worse all the capability is already physically in that base model but you pay to unlock them..
The suspense...
Part 3 in an hour or two? Please? Pretty please? Pretty please with sugar on top??? :-)
I'm still waiting for the electroboom moment!
Watching intently...PS in my R&S spectrum analyzer apparently is dead as well!
Switchmode powersupplys are sooo complicated q.q i have 3 that i can't repair because i don't know what's exactly wrong with them.... Tow of them have a deat starting circuit but maybe i can fix them now with your knowledge thank you :)
They are not so complicated, but they very often suffer from the problem that they cannot work unless everything is working OK and when one part fails it is difficult to do measurements because the entire thing is just dead.
Also, one failing part may destroy other parts, and the generic way of solving problems (check if parts have failed an replace them) is not very successful on those supplies because usually you will first replace the parts that got blown by other failures, so the replacements will just fail again.
@@Rob2 exactly ! cascade failures are the best !
@@Rob2 Well said! You need soft start and shutdown to ensure that energy stored in inductance can safely run out. In a failure a sudden change in current causes high voltages according to V = L x dI/dt blowing up every semiconductor in sight!
There are however testing tricks that can help: Use a Variac and try to run the thing @ reduced input voltage. Override the control circuit with a signal generator to see if the power chain is intact (running in open loop).
Last test the circuit @ full voltage and load with control loop closed while hiding under the desk :)
I’ve had some luck with substituting 9V batteries (sometimes 2 in series) for various “standby” voltages within switchers. The fates were kind and when invariably one of such kludges would get 300VDC across the terminals, it didn’t cause any major nor even minor body damage. I did run a power supply in my fridge with a slightly flat 9V battery in place of a 12V Zener that had failed. Overnight I found a replacement part, and the battery got a bit of trickle charge to recover :)
Wonder why the complicated this PSU so much ? In the end it's just producing normal range Power Rails.
nice hp calculator :)
@CuriousMarc, have you recorded anywhere, on video or on "paper" your background in being interested in electronics? like maybe from when you were young?
This one? ....ruclips.net/video/fK-IZuIonnY/видео.html
You can't end on a cliff hanger !
Back when I worked on the bench we called people who just changed endless components "farmers" or "change artists". It was meant as an insult.
I would not call that a rant, more an explanation why you do it the way you do it and also as an advise why this would be the better way (learning, saving parts, sometimes something that can not be swapped, etc).
I agree mostly with the "rant" What you do is the proper way (certainly for this situation), but it is just not economical in many cases. Capacitors are cheap (sometimes so cheap they fail premature) and they are easy to replace. So shotgunning them makes economic sense in a lot of cases. Also depending on application compared to a resistor they have quite the limited lifetime which is specified in the datasheet as you must know. 80's home computers (classic macs, Xbox clock battery) are full of leaking (literal) batteries, corroding the circuit-board. For a time period failing caps were the number one cause of failing main boards and computer power supplies. Then there are the paper-wax caps in tube equipment. They suffer moister ingress. Replace on sight or risk smoke. A few might be fine, but do you really want to keep returning to the same job over and over? Often I consider replacing them all not so much repair but also preventative maintenance. I do agree that this proper analyses is much more interesting to watch. O and before I forget the example of the Rifa safety caps. Yellow transparent housing, very specific series. They swell up crack the housing and then blow up. I found good ones, but never left one in. Quite sure the customer rather not come back twice....
"Toss a coin to your Switcher ..."
Another cliff hanger
Given the 3rd part is coming, something tells me that fix alone was not enough to get the thing working.
I think there will be like 6 or 8 parts... :-)
Wer misst, misst Mist. (German engineer's saying. Means "He (or she) who measures, is measuring crap") Which basically means "Know the limits (and quirks) of your measuring gear and keep in mind it can affect the circuit you're measuring"
(I'm kinda disappointed I can't give this video more than one thumb up)
senilyDeluxe "kurz nach fest kommt ab" is another good one :)
why not just isolate the whole instrument with an isolation transformer.. Am I missing something here..
Absolutely, you can do that too. That’s what most people would do actually. But that's not nearly as powerful as using a differential probe, where you can probe absolutely anywhere, completely off the ground, the two sections at the same time if you wish. Unfortunately I ran out of common mode margin. I got the x100 attachment since then....
CuriousMarc It’s probably good that there was no hard protection against exceeding common mode limits. I’ve had the dubious pleasure of using a probe that had some unforgiving fast-acting semiconductor clamps that protected the input stages from common mode overvoltage. The clamps were totally up to their task. The fault current they shunted was sufficient to vaporize the tips of the probe. Other than that, the probe survived unscathed. My corneas were not that happy though - whether it was the UV or the rapidly condensing metal vapor sent their way. Live and learn - and it helped that I was only about 20 at the time.
Why didn’t you replace the electrolytic caps 😂😂😂😂 because the damn thing Is detonating mosfets 😯 maybe your should just replace the power supply 🤬🤬🤬🤬🤬🤬 it’s got 6000 rails and two that are variable!!! 😳 what kind of TV did you say this was out of ???? ☢️ 🍄 ☁️
"Uncalled for advice"? :)
@@Citronitroify You leave this troll alone.
Three idiots do not know what is a nice video... Probably preferring car crashes or motor explosion compilations...
Keep going Marc! I know what it means to understand how these things are working and how to repair them. As you say, the world will always be divided in two categories : people who think that repairing is just replacing a part or a complete device. And the others...
Obviously you just haven't bench thumped it hard enough yet. :3
Man plans; God laughs!
what about just replacing EVERY component on the board? might be the fastest solution?
Usually after replacement like that you will find out that the board itself has a shorted/broken trace in the middle layer)
I think this is more of gaining an understanding of whats failing and causing the problem. Hopefully when you find it that's much more rewarding than shot gunning the whole board. Maybe in a fast turnaround customer is paying situation then that can be an effective approach as would be just replace the board. The cost / availability of board like this though, not first choice.
And what about the transformers? Winding by yourself?
hahaha, i saw got blow
I'm the second to watch.... :)
And first to comment! You get a free broken driver IC.
@@CuriousMarc 😂
First comment. Do I get an interesting or funny bit of some kind? 😁 I really like your videos. 😊👍
I am not sure who is first, seems like @Wilian Henrique Rosada clicked faster. But there is plenty of broken vintage bits to distribute from this supply. How about you get a free vintage kickstart pulse!
7th
Ben heck doesnt like this