Any practical examples of success repairs

[Jane]

Are there available( anywhere) any successful repairs of switched-mode power supplies?
I found a few on YouTube but they were rather simple( e.g.changing dried capacitors ). I would like to see( and learn)how to solve more serious faults and not those trivial ones that can be seen at the first look.
Thank you.

[stj]

Re: Any practical examples of success repairs

shorted diodes or fets are common.
cracked soldering is also common.

[retiredcaps]

Re: Any practical examples of success repairs

Some of these channels have SMPS repair beyond the simple bloated capacitor, but none that are dedicated.

https://www.youtube.com/user/TheSignalPathBlog/videos

https://www.youtube.com/user/norcal7...ow=grid&view=0

https://www.youtube.com/user/Maxxarcade

https://www.youtube.com/user/ATVVideoProductions/videos

https://www.youtube.com/user/FFcossag/videos

https://www.youtube.com/user/JonnyFixy/videos

https://www.youtube.com/watch?v=NoGl7oeh7eU

http://www.repairfaq.org/sam/smpsfaq.htm

Sorry, I don't recall which exact episodes, but you can look and read through the titles for yourself.

[CapLeaker]

Re: Any practical examples of success repairs

to add to sti's comment:
open resistors, or resistors that changed value outside the tolerance. PWMs that don't switch. Blown up gate drive circuit (when the Mosfet is shorted).

[Jane]

Re: Any practical examples of success repairs

Thank you for the replies but this thread is not closed :-)
So if you find an interesting repair ( preferably describing a procedure from the beginning to a successful repair)
It would be appreciated.

[Marianelforum]

Re: Any practical examples of success repairs

I do not know of repair stories on youtube ( did'nt searched for any ), but speaking from my own experiance, there are sometimes psu's that suffered too much damage to be worth fixing, just a few days ago i gave up fixing a rather interesting PC power supply because of the extensive damage, many thin copper traces practicly vaporised, traces that lead to many very small SMD components ( you can imagine the damage ), many power semiconductor's exploded, even some "coocked" power traces... So i have decided that it is not worth fixing it.

Many well designed psu's have built in fail-safe's that can limmit the damage they can suffer from normal use especially when caps die ( and often they are the cause ), or even on some abuse. So you can end up sometimes with an easy fix.

[zx8401]

Re: Any practical examples of success repairs

Thank you for the replies but this thread is not closed :-)
So if you find an interesting repair ( preferably describing a procedure from the beginning to a successful repair)
It would be appreciated.

I would say a basic knowledge of the typical blocks used in power supplys is very helpfull, there are many schematic diagrams on the outernet, look at most and you will see common designs/patterns.

Pattern recognition is built into all of us, wear it out looking at schematics .
Basic knowledge can get you a loooooooong way lol.

[keeney123]

Re: Any practical examples of success repairs

I would start with something like this http://www.learnabout-electronics.org/PSU/psu30.php and learn each section and how they work. If you are unable to understand something then post it as there are many people on this sight that have a good understanding. Once understood, then you will need to have equipment to help you troubleshoot the power supply.

[budm]

Re: Any practical examples of success repairs

Hers is one of many on BADCAPS.
https://www.badcaps.net/forum/showthread.php?t=51797
Post #1~28.
Here is the success repair with 64 cents part, no visual sign of damage.
The common test that I always request the OP is to find out if we have DC on the main filter cap or not after the visual inspection and simple fuses testing.
But the the bottom line is that you need to know the basic electronics, about the components, how the power supply functions (in this case since you want to learn how to go about fixing the power supply), and lots of on hand experience. You have to at least be able identify each section of the power supply board even if you have never seen the board before, when you have been doing long enough you will see the pattern.

OK, it is the same board.
You need to do resistance test on the Diodes D10, D21 (mounted on the heatsink), D22, and D23 to see if any of them show low resistance in both directions.

You probably wonder how I come up with that question for the OP about checking those particular 3 diodes but not ALL the diodes on the board.

[stj]

Re: Any practical examples of success repairs

i changed a fuse.

[everell]

Re: Any practical examples of success repairs

Thank you for the replies but this thread is not closed :-)
So if you find an interesting repair ( preferably describing a procedure from the beginning to a successful repair)
It would be appreciated.

You asked for it, so here is the story of a smps power supply that was "burned up".

https://www.badcaps.net/forum/showthread.php?t=9660

[CapLeaker]

Re: Any practical examples of success repairs

There are some I posted too. Also look at the NT5B01, there were a couple of funny behaving PSU's in there, that worked for a bit, then shut off.

[Jane]

Re: Any practical examples of success repairs

Thank you ALL for the links
What measure equipment do you use to check transformer's windings?
Only LCR bridge? I also read about Anatek Blue Ring "Q" Meter Kit .
Does anyone use it?
Is it worth buying it?
Thanks again

[budm]

Re: Any practical examples of success repairs

I do not have the Blue ring tester, I use SENCORE LC-75.
http://preher-tech.com/documents/tes...ormersinlcdtvs

[Jane]

Re: Any practical examples of success repairs

@budm: Thanks for the reply.But can you please explain why LCR bridge is not enough?
I still do not know why someone uses a device like a blue ring tester( or similar) and not LCR bridge instead.
Thank you

[budm]

Re: Any practical examples of success repairs

If you want to use LCR then you need to know the inductance of a known good transformer to see what inductance you get and compare it to the suspect bad transformer that has some shorted turn.
You can try that experiment with two transformers with same spec., then make one with shorted turn and one without and see what reading you get on the LCR.

[budm]

Re: Any practical examples of success repairs

BTW, what tools do you have right now?
And what kind of experience and knowledge base do you have?
Able to read schematic?

[stj]

Re: Any practical examples of success repairs

Thank you ALL for the links
What measure equipment do you use to check transformer's windings?
Only LCR bridge? I also read about Anatek Blue Ring "Q" Meter Kit .
Does anyone use it?
Is it worth buying it?
Thanks again

blue-ring?

that's the bob parker design.
i made my own on stripboard.
http://members.ozemail.com.au/~bobpar/fbt.htm

[michael dranfield]

Re: Any practical examples of success repairs

I made this 16 years ago before the importance of effective series resistance had been fully appreciated.

[Jane]

Re: Any practical examples of success repairs

@budm: I have DMM, LCR bridge with ESR meter, oscilloscope. I work with a company that repairs satellite receivers and mobile phones.Yes, I can read schematic.
@stj: Thanks for the pdf file