all ATX power supply lost power (aging)

[laser]

I noted that all ATX power supply start to lost power after certain time
in all cases all lost power in the 5v line and the 3v line and never lost power in the 12v line
this aging issue makes the ATX power supply unusable due low voltage in those lines causing serious problems in the motherboard specially in the gfx card

of course there are not the caps which filters 5v and 3.3 v lines because I replaced with good caps in all cases

so which one is the guilty of this aging problem?

-coils ???
-small electrolytic caps (those rated from 1 mf to 220 mf) ???
-the 2 big caps which generally are 200 v / 470mf or 560 mf ??

can anyone explain plz

[b700029]

Re: all ATX power supply lost power (aging)

Check the rectifiers.

[laser]

Re: all ATX power supply lost power (aging)

Check the rectifiers.

they are always ok

but... do you mean those rectifiers double diode which are fast and named schottky ?

[Agent24]

Re: all ATX power supply lost power (aging)

they are always ok

but... do you mean those rectifiers double diode which are fast and named schottky ?

Yes the output ones can fail.

If the primary rectifiers\bridge fails, then nothing will work.

[laser]

Re: all ATX power supply lost power (aging)

Yes the output ones can fail.

If the primary rectifiers\bridge fails, then nothing will work.

the power supply I'm testing is working
the problem is the output on 3.3v is 2.9v
and on 5v is 4.6v
there is something worn and the problem are not the caps ( I replaced all by good chemicons)

maybe the problem is the schottky diodes which are fast and lost speed

what do you think guys?

[tom66]

Re: all ATX power supply lost power (aging)

the power supply I'm testing is working
the problem is the output on 3.3v is 2.9v
and on 5v is 4.6v
there is something worn and the problem are not the caps ( I replaced all by good chemicons)

maybe the problem is the schottky diodes which are fast and lost speed

what do you think guys?

Possibly the primary-side capacitors, they went bad on a PSU of mine.

[Agent24]

Re: all ATX power supply lost power (aging)

the power supply I'm testing is working
the problem is the output on 3.3v is 2.9v
and on 5v is 4.6v
there is something worn and the problem are not the caps ( I replaced all by good chemicons)

maybe the problem is the schottky diodes which are fast and lost speed

what do you think guys?

OK now that is a different story - when you said earlier that "in all cases all lost power in the 5v line and the 3v line" I took that (and I think most people would) that the 3.3 and 5v lines were completely dead.

Now you're saying they are just low.

In that case it could be the voltage regulation circuitry is faulty and keeping the voltage lower than normal.

Post photos if you can, this can help a lot.

Possibly the primary-side capacitors, they went bad on a PSU of mine.

Yeah they could be bad too