Switching power supply repair. Testing transistors & diodes.

Today I show how to fix a switch mode power supply (SMPS). In this case it was a 750W ATX computer power supply (a 2-switch forward topology with an active PFC). I demonstrate how to find faulty components. I mostly focused on testing semiconductors (transistors and diodes). As a bonus, I show some waveforms on my oscilloscope and demonstrate the operation of the 3.3V and 5V regulation with saturable inductors (at 24:42).
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[@jooch_exe]

I've been watching this channel for a long time now, but this is without a doubt the best video on PC SMPS repair. And completely true to the channel's name, diodes went wild indeed. Well done! (subscribed as of now)

[@Conservator.]

DiodeGoneWild has done quite a few SMPS videos one or two years ago. Not just the dodgy chargers.

[@hullinstruments]

Hope he does more like this

[@liamspencer2641]

Hey DGW! I'm a junior technician for a power supply company, and I just wanted to say thank you for the in depth troubleshooting. This is literally my job everyday and you're really helping me by sharing your experience!

[@Earthling418]

Epic level circuit analysis, reverse engineering and diagnostic evaluation. Also most pertinent detailed explanation. Love every presentation. Please, keep it up.

[@raffaellobottoni871]

Here you see the true knowledge and experience in electronics! In other words , The real Know how! Thumbs up! You are a master! 👍

[@gamiwv]

I hope that someone would have the idea to encourage his/her students to study with these videos. My compliments DiodeGoneWild

[@Tigrou7777]

The schematics you provide each time (and related explanations) are a huge plus and is what make difference with most repair / DIY channels.

[@noway4040]

Hey, I am just passing by to thank you for making your videos and you channel. I just recently fixed my broken PC power supply using all that I learnt from you.

[@alupci]

This guy got me 26 years back when doing high school. Back then we lack practical explanation in our country. All we learnt was theory and when he started explaining transistors, diodes etc the glitches started happening in my head. Perfect explanation!

[@filenotfound__3871]

26:12 I have the exact same PSU with the exact same fault Do more PSU repairs, they are the best to learn electronics.

[@Zebra_Paw]

i completely agree

approx was extremely low quality and cheap, it's not even worth disassembling, just throw it away

[@filenotfound__3871]

@ I did like a year ago when it happened

[@Zebra_Paw]

LOL

[@bitelaserkhalif]

That particular psu looks like junk anyway

[@philippezhang]

repairing SMPS is just a piece of cake for you :) Thanks a lot for detailed explanation and ESR meter extra usage

[@trueforum378]

Hi there. I saw your video for the first time and as an electrical engineer I am VERY impressed with the depth of your knowledge and experience! GREAT JOB. I am curious how to you get to that level of knowledge. Hands on alone will never get you there! very impressive. Thanks for the efforts of putting such valuable videos together!

[@franzliszt8576]

Hi diode your videos on smps are the best and you explain them so good!

[@Eldi-Kwetu]

Wow learned a lot from a true electric engineer working on a disaster to diagnose the problems. Just like my medical profession. Lots of things to think and interface. Thank you for sharing.

[@hernancoronel]

Hi Diode, thank you for the great video!

[@arthurmead5341]

You're welcome!

[@TNT5021]

One of the best pcb fixing i saw in weeks

[@hoggif]

Use of ESR meter for diode measurement is quite clever or at least something I'd not have thought of.

[@felixcat4346]

Yes, you could also use a NanoVNA. Basically anything which puts out a high frequency to bypass the inductor.

[@deadgamer9808]

@@felixcat4346 hey bro can you help me regarding a problem with my smps i have a pc and i recently troubleshooting it for some reason during which i have found that my psu gives 24 volt ac along with 12 volt dc in output of 8 pin gpu connector is it normal to have ac output along with dc in power supply thanks

[@erminbajric4633]

@@deadgamer9808 Don't rely on cheap multimeter readout.

[@deadgamer9808]

@@erminbajric4633 ok :)

[@seckinseckin3919]

@@felixcat4346 and how about using IV Curve Tracer instead of NanoVNA ?

[@memylastname9972]

This video really helped me to understand how to test components whilst they are still on board and the problems deciding what the test results are telling you. Smps seen to be in everything and I have always hated working them. But since watching several of your videos I am a lot more confident repairing them. Thank you.

[@hullinstruments]

Danyk… I would super really appreciate it with a cherry on top if you could do more general troubleshooting videos like this. Its awesome what’s possible with than $100 in test gear. Like a handheld oscilloscope, multimeter, cheap in circuit ESR tester, $5 USB logic analyzers, $30 curve tracer kits available online

[@hullinstruments]

Also the cheap five dollar USB soldering irons like big Clive has shown, or better is a $40 KSGER t12 station. You can even get a “laptop style” variable power supply. Mine was about $25 and is adjustable from 0-32 VDC at a couple of amps, and came with about 50 different interchangeable tips including plain jumper lead alligator clips, Several different types of BNC adapters, pretty much anything you could think of. Obviously that doesn’t compare with my professional lab and equipment, for around $100 that stuff will pretty much accomplish 95% of every repair. Seriously.

[@hullinstruments]

Sorry to bug you and add another comment. I’ll try to add other things that come across my mind which makes troubleshooting 10 times easier. Maybe all this rambling will help someone. Another thing very useful if you don’t have a thermal camera is the flux and vaporizer trick big Clive showed a few weeks ago. Others also have shown it on KZbin. Will easily show hotspots on the board. Also some thing I find very useful is one of those cheap $25 wireless/Wi-Fi microscope’s. It has an internal rechargeable battery and is HD quality, with surface mount LEDs around the ring of the front of the lens. I have a few nice stereo microscope‘s in my lab, one is an M scope Asian model that I really love, and one is a very nice Zeiss from the early 90s. But honestly I grab that little $25 wireless microscope more than anything, to help spot shoulder joint issues and other things. Mines about the size of a lipstick too but you can also get them that are as big around as a small pencil, like something you would use to check the insides of your ears. Those can even see under BGA chips and find issues in other type to reach impossible to see areas of the board. Another cheap and ingenious way to find issues, is with a cheap UV blacklight flashlight. It will reveal things like capacitor fluid leakage, charred or heat damaged parts of the board, or where a component failed violently and really didn’t leave a trace because it vaporized… But it left a little spew of a vapor on the board which will be seen under different wavelengths of UV you can see many things that are invisible with regular lighting conditions. I prefer 365nm but it’s good to have several different wavelengths, especially these days they’ve become inexpensive. UVA, UVB, and UVC led lights can we had for just a few dollars each. They will eliminate many different issues on the board, some of which respond better to certain wavelengths so it’s good to have all three. I have a multicolored little $5 flashlight that includes 365nm uv, bright red, green, and then of course white. It constantly comes in handy and the UV light can even shine through the PCB material from the back, revealing issues or damage that might be between layers of the circuitboard, especially on multilayered boards.

[@DrBeat-zs9eb]

This was very interesting! Looking forward to the next video about PSUs.

[@marekquarda8023]

Vynikající práce. Zároveň bych chtěl poděkovat za vaše videa, která mě mnohému naučila. Děkuji moc. Marek

[@DiodeGoneWild]

Díky, není zač :)

[@abdelatifmariche8771]

my best topic on your channel

[@Geniusinventor]

I was waiting for a power supply fix video for very long. Thank you!!

[@richardnanis]

Great explanation and very smart analysis and repair of circuitry! Very clever to use the ESR-meter to test the semiconductors in circuit! :-) Nice you could repair and fix it! I really hate removing these big heatsinks and components on them - it takes a lot of time and patience. I have to admit i am not that fast and smart in analysing the problems. I always have to look twice if i got the correct pins for measurement and have to think about where is gate, drain and source and what circuitry could cause what kind of side effects in measurement.

[@bulwinkle]

It is good to see the matt back heatsinks. So many are left as bare Al, presumably because some marketing dummy thinks it sells better.

[@juntendo6104]

WOW so much effort put into fixing the SMP!

[@Jumansa19]

Like always - great stuff - also like that you use more simply and in best sense "cheap" equipment - no expensive dreams, no "stylish" money robbing brandings

[@Basement-Science]

A great way to test transistors is to use a 3-terminal transistor tester. They will actually control the gate/base of it and make sure you dont accidentally turn it on or off. Plus they can measure capacitors and inductors and all that and get their actual values. They are super useful.

[@Broken_Yugo]

Yeah those cheap transistor/ESR testers are great for close enough hobby/repair work, probably the best use of a ATmega328p I've seen.

[@lmwlmw4468]

No doubt about it ....DiodesGoneWild......and nothing like de-soldering the components........Great video.

[@DIYwithBatteries]

Diodes are really going too...wild lol Thanks for sharing mate. 👍

[@jkobain]

I understand nothing in building/repairing of such devices, but the video is very interesting. Thank you!

[@JAINUL_HAQ]

I love your videos very informative and your accent is just lovely.... I worked with some chip Chinese Computer SMPS they are fireworks can triggered at any time with their own

[@informediatech-bruno5766]

I LOVE when the DIODE GOES WILD

[@leozendo3500]

I learned about measuring mosfets. Thank you.

[@German_byte]

Thanks

[@giovannimarino4464]

Thanks for sharing. I think that should also interesting the ripple measurement just to see the power supply quality ...

[@hugoegon8148]

Nice trick to use ESR meter. 👏🏻

[@mcg6762]

Very nice video! Love your content, especially the repairs! Greetings from Sweden

[@BomJimmy]

Thanks for showing good use of ESR meter.

[@OnStageLighting]

Love SMPS repair mysteries. Got an odd one on the bench here. Inverting arc welder that took out a winding on the startup circuit but no obvious short. Have lashed the winding back together, but still not brave enough to power it until I've found more info on why it burned out. It won't be fixable if happens again. Power MOSFET seems ok with a basic meter test, although charging the Gate doesn't seem to last long. Avalanche diode tests OK, but only a DMM test.

[@OnStageLighting]

PS, always discharge D-S before testing... ;-)

[@speekergeek]

Thanks for providing this content! I work in a similar field and enjoy the process of troubleshooting :)

[@tako1257]

These videos are great for learning, they help me with engineering studies, but could you do some videos that specifically focus on edjucation? Thank you for all the free quality content!

[@grenzhochspannungshindernis]

you should get 100 millions subscribers just for your accent and another 100m for you content.

[@TheRintincola]

Interesting video with lots of technical information! With this video I learned some new things!

Haha... it’s the same problem in my psu (Corsair 750w TX). Blow up many components and when I fix it the 12v it’s short as well. Now i'm waiting for the diodes to arrive.👌😅 Great video. Peace out ✌️

[@hullinstruments]

It would be awesome if you could make a few more of these general troubleshooting videos.

[@gizmosk2996]

Finally some quality stuff on KZbin! The perfection would be to show where you put the probes of the oscilloscope before each test. PS: if the video would be in Czech or Slovak this would be : na nezaplatenie ;)

[@saarike]

Really great repair with precious information! My humble thanks. 👍

[@Krisztian5HUN]

more psu repair plz, i learn a lot from this vid...

[@Miata822]

Great video! Love the level of detail.

[@ziggyironic]

Thank you for making this video and sharing your knowledge. This was very interesting and helpful.

[@sidewinderam9m]

These videos are great, patreon for life thanks so much!

[@louisroux8517]

Thank you it was very educational. I love the tip on a "cheater meter.😀

[@Atetus94]

Clever use of that ESR meter :)

[@johnmcgiv1]

This was a very very interesting video thank you very much. I would really appreciate a video and more in depth use of the esr meter testing diodes transistors and any other components it can test in circuit great idea.

[@Rocco_v]

Excellent detail, Nice kitty, Thank you!

[@zx8401ztv]

Tricky testing in circuit. I just lift one leg up and test the part, but i should have lifted the component leg and not my own lol :-D I test large mosfets with a bulb for a load and a resistor to drive the gate. Same for scr's. Good enough for a rough test :-D

[@andiyladdie3188]

Very nice fix and explanations. I have to say that those primary side, ultrafast diodes are bloody expensive to buy 😅😁

[@Shmbler]

Nice Job. I guess I have to order myself a pile of broken PSUs to repair. Should be fun.

[@Zebra_Paw]

The other ATX is also going to be very interesting. I did the same with a 24V 15A SMPS (supplying 230V with the switch set to 110V), and it just blown the mains capacitors (their were two of them because it was a HalfBridge power supply)! The transistors didn't blow up. Oneof them blown up two weeks later because the diodes that use to get rid of the inductive spikes were open circuit (i think there were fake diodes because it was a cheap chinese power supply). I replaced them and both transistors, because i had the same reference as the blown one but it was not the same transistor model so as they are in a HalfBridge i had to replace both for them to be identical.

[@JunPVlog]

Good job sir thanks for sharing new supporters here

[@electronic7979]

Very helpful video

[@Waasil]

Thank you very much for this educative video, well done. really nice video

[@miscojones35]

5:57 I once blew a filament lamp by doing that to a 450V cap

[@DiodeGoneWild]

Well, it's better to use 2 lamps in series :)

[@barnabasnagy9595]

Wow... How much watt was it?

[@Conservator.]

@@barnabasnagy9595 I think he meant discharging the large capacitor. Wattage wouldn’t matter too much compared to the capacitance, given the 450V.

[@barnabasnagy9595]

@@Conservator. I meant the wattage of the lamp, because I think it's harder to kill a 100w lamp than a 40w one.

[@ranjithalumullithody]

Great video 👍🏻

[@mostlymotorcycles.]

As always a most interesting and informative video.

[@FindLiberty]

Like a LASER BEAM... very good sir!

[@norvinsakiral4450]

I learned a lot from this man.

[@vhm14u2c]

Wonderful TS’ing, thanks for sharing!

[@weerobot]

Cool use of The Capacity Meter...

[@curiosityseesomethinginter9116]

you are a really good singer too😊😊😊😊😊😊😊😊

[@tobitechboy1461]

Hey mr diode! Thanks!

[@Basement-Science]

So all this just from bad assembly on a heatsink. All it took was to tighten the screws properly and it would probably last many years more.

[@electronicwaves]

The OEM is CWT, notorious for quality issues in the assembly and bad soldering.

[@Broken_Yugo]

That's the thing about super cheap off brand electronics, they pass the savings from having no QC on to you.

[@1pcfred]

PC PSUs are not designed to last many years. There's parts in them that degrade over time. Namely the output filter capacitors. Tier 1 PSUs you might get a long service life out of. Seasonic is offering 12 year warranties. Generic PSUs you're lucky to get 5 years out of before they start putting out damaging ripple.

[@rfmerrill]

If you want reliability you have to use server PSUs, from companies like Delta or Artesyn. They are designed to be put in a rack and left there, and run for decades nearly 24/7

[@Basement-Science]

@@rfmerrill Not sure about that. Server supplies are designed to be swapped easily in a redundant configuration, not to last forever.

[@worroSfOretsevraH]

Hi. Modern high power PC psu's usually use an LLC topology. Could you make a detailed video on how they work? Thanks.

[@rfmerrill]

@ 15:32 Edit: oh wait never mind they are not in parallel, they are connected differently. Worth mentioning that the diodes are in parallel with the body diodes of the FETs. The external diodes are probably placed so that there is less voltage drop and/or to not dissipate extra power in the MOSFETs.

[@Mitgardxxl]

Very interesting. Thank you very much.

[@AmateurRadioAwesome]

Thank you for the epic explaination!

[@pishta-ux5qz]

Nice analysis

[@piconano]

You need to build yourself an Octopus curve tracer. You can't fool them easily.

[@merwynvincent]

There will definitely be a day when singers would kill to have this voice auto tuned for them!!!!!!!!😜😜

[@SonuKumar-ul9xv]

You are a genius

[@Electester]

Excellent material!

[@عمارةحامدي-ذ7غ]

think yo for the video I learn a lof of things

[@PrajjalakChattopadhyay]

Hot barbequed double diodes, garnished with white thermal compound sauce, served loose on a big black heat sink... sounds yummy!

[@michalcerny455]

Wish my power supplies repairs went this nice. The ones i'm getting usualy have blown insulation on the transformer, what in most cases is not shown by multimeter, but apears only when powered. And yeah try to rewind transformer mudded with epoxy... :D :( But anyway great vid!

[@SuperBrainAK]

you should get a DE5000 LCR meter, it will be able to measure the inductor and very low resistances to measure the traces low resistances.

[@ScienceLab760]

hi thanks for share, very interesting video i always learn something new with your content

[@ToleSan]

Hi danyk. I hope you soon explain about that gate driver transformer.I dont know how the right winding (what materials, EE, or toroidal ferrite, how much the windings, how the inductance..). By the way, i have made two switch forward welding inverter based on your schematic in your website. Thats very powerfull and usefull (the video is in my channel here)

[@sanjeevpatel4828]

Very nice information bro

[@madeintanzania2995]

Thank you sir, your on fireee

[@endurancefriday2215]

Nice keep up the good work.

[@waelelkholi3406]

Hello, Thank you for your video :) .I have a 1600 watt power supply that is not outputting 5V from pin8 (PGO) of ST9S313 ( which is a PC POWER SUPPLY SUPERVISOR ) . All other voltages of the 24 pin connector are ok. I can't get the IC or equivalent, can I just bridge 5v from anywhere on the board to this pin ( it is pin5 on ( the grey wire ) on the 24 pin connector.

[@FernandoRodriguez-uo2fk]

Hello!, why for the final test you use the 300w lamp instead of the 100w? I’m trying to fix a similar power supply and using a 42w lamp, it turns fully on when I power on the supply.

[@KaisUK]

Dude I love your videos but it would be amazing for us novices to have a visual reference to what components you are referring too when naming them and testing them just by pointing to the component on the opposite side before flipping the PCB to test the PCB traces or removing the diodes. The video was so easy to follow but I got lost because of information I lost because of it :(

[@iljahyncica7100]

...and now let's explore the disaster :) :) :) // great videos - hat down !

[@AxellTh]

I have a smps charger for power tool. No life on the cold side. Checked every component exept the transformer and a 6 and a eight legged chip. How is these components checked?

[@johnmcgiv1]

Hi back again just tested 2 diodes with same esr meter you have there is a coil in the circuit. both diodes tested

[@DrZipZwan]

I got a problem on mine, smaller model (60W). When I turn it ON, the small led near the output is blinking constantly and output is fluctuating. Nothing is blown inside. I checked main Transistor and Main Output Diode (>

[@Speeder84XL]

Very nice and interesting

[@davey2k12]

Ha ha my mate switched the voltage selector to 110 while it was plugged in to 240v it was old desktop pc what a bang that was 🤣🤣🤣

[@adrian_sp6def]

Do You make an video explaining an two switch forward topology? Can not find it