I've fixed all kinds of SMPS problems – both minor and major ones. And in all cases, I would isolate the problem as soon as possible. I suggest you do the same.
You must be able to identify exactly which section of the SMPS is causing the issue. You'll save a LOT of time this way!
Now, if you have an SMPS that isn't working, I think the source of problem can be attributed to the following:
Damaged SMPS components…
Inspect every section carefully to see if there's any broken/loose/totally detached component. Look at the primary section. Is the power IC working correctly?
Take out your UC3842 IC Tester unit to measure the power IC. Damaged capacitors is also one the most common SMPS problems so check those as well.
Main circuit board problems…
Noticed the power supply LED blinking/dim/ shutdown? If yes, then you should measure each component in the main area of SMPS. Aside from the main section; do check the secondary area as well.
Fan problem…
Trying to repair an ATX switch mode power supply? Inspect the fan! The fan is vital for sucking heat from the components. If the fan doesn't work properly, then excessive heat will occur, resulting in complete shutdown of your ATX SMPS.
Soldering problem…
Well, this is definitely not one of the most common SMPS problems around…. However, fairly big sized components can be found in most switch mode power supplies and soldering them can be rather difficult.
So, just check the solder connections too if you find nothing wrong with the components…
If you need to make adjustments to the connections and you're not too confident of doing so, then I suggest you test your soldering skill on a dummy circuit board first.
The Biggest problem for Novice technicians
The circuit design of switch mode power supplies is more complex than their linear counterparts. And to worsen matters, there is a serious lack of ‘take-you-by-the-hand' guides on how to troubleshoot and repair SMPS in the proper manner.
This I believe is the biggest problem for novice technicians. I know, because I went through the same experience.
Now, you can avoid this problem by visiting a website called SMPS repair information. I think the exact link is right here.
That's where I discovered a thick downloadable manual with step-by-step photos on solving various SMPS problems. Go ahead and follow the above link if you're interested in downloading it.
