Reply 20 of 22, by momaka
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boby wrote on 2025-06-06, 15:36:Yes, I get what you say, and didn't say that I will replace all caps with one type, just asking what would happen. Trying to learn something here 😁
Ah, OK.
Well, if you use a capacitance value that is lower than what was there previously, then the filtering on that rail won't be as good anymore and you will get more noise on it - possibly to the point where it causes your system to crash. Really depends on how far you take it with the reduction and how sensitive the PSU filter circuit was to begin with. For some, up to 50% reduction may not cause issues - not outright anyways. But for some, even a drop larger than 20% can be problematic. So in short, lower capacitance = not desirable.
On the other hand, it's -OK- to use capacitors with higher capacitance than the original... within reason, of course. Generally speaking, and at least from my own experiments too, I can confirm that going 2-3x the capacitance will rarely cause problems - but note that this is ONLY in regards to the output filtering caps. When it comes to any small capacitors that have other functions, going up or down on the capacitance by more than 50% may become problematic (e.g. if the circuit has a 10 uF cap somewhere and a 22 uF cap is used, that may cause issues.)
boby wrote on 2025-06-06, 15:36:The part for 5 VSB, I didn't get properly. How to find this cap? Why is it importand to be replaced if it look ok?
See upper-left corner of the PSU's PCB in this picture of yours:
download/file.php?id=220405&mode=view
The two small caps under the AC wires - one of them is likely the 5VSB start-up/run/critical cap, while the other is likely the main PS run cap.
These small caps can often go bad without bulging.
Alternatively said, a cap that is not bulging doesn't mean that it's still good - particularly the case with non-Japanese caps.
Brands like CEC (PCE-TUR/PCE-TUL) are generally relatively OK, though. But whenever I recap old PSUs, I always check these small caps anyways. Every once in a while, I do run into bad ones that don't show any exterior signs of being so.
If you don't have a cheap ESR meter to check them, then it's usually a good idea to replace some of these - or at least the ones that are critical, like the 5VSB startup cap in 2-transistor 5VSB circuits. Of course, only do that *IF* you have access to quality Japanese caps. Otherwise, I'd be more tempted to trust the original PCE-TUR/TUL caps in this PSU than no-name Amazon/online garbage.