PSUs without -5V rail

[Zubkover]

Hi there!

Lately through my hands are going A LOT of PCs that tend to have ONE common issue.

They would turn on, but no POST, no vid out, no beepcodes, complete LIMBO.

I test their PSU on the cheapo chinese tester - I get no response LED from -5V rail.

I change out the PSU - PC starts to work normally again.

 

The issue became such a big thing that I have literally at least 1 or 2 PCs like that every weekend, and I don't know if there is any fix to that, since they look fine otherwise. Moreover I actually acumulated aprox. 1-1.5m tall tower of such PSUs on my shelf.

 

Anybody has any fix on this?

 

I'd be happy to receive any help, thanks!

[Billy_Mays]

Tinker with the PSUs 

dont you very much could kill yourself and that's lots of PSUs almost as tall as me

[Pesukarhu]

Either test them with a multimeter, or get a tester that reads out the voltages. Apparently modern stuff doesn't need a -5v rail (my psu doesn't even have one), so it may also be that whatever broke the -5v rail broke something else too. Or older hardware. (just guessing - maybe the drive circuitry cant regulate the voltages under load?)

 

Maybe take one apart (the longer it hasn't been plugged in for the better) and look inside for skidmarks, corrosion, swollen capacitors etc. Hot glue around larger components is normal. Be careful, some of the capacitors may still have charge left.

[Mira Yurizaki]

What PSU do you have that has a -5V rail? -12V is part of the ATX standard but not -5V. Unless you mean the 5V_SB?

 

EDIT: Ah, there was a -5V until ATX 1.2 for ISA slots.

[Zubkover]

The tester is labeling it as -5V, but even those without this good old white wire are ligthning up the LED for it.

So yea. That fact makes me confused.
I "tested the tester" itself on eveything from old PSUs to lastgen Tacens, Chieftec, Coolermaster and so on. No -5V on tester -> no POST on most boards, no beep code, no video, nothing. With the one exception of that one Chieftec that actually can power everything that is plugged into but still has the same "error".

For some reason after replacing the PSU PCs start to work all properly, even though that the rail is supposed to go "by name" only to ISA slots, and I had this issue on some LGA 115X boards, and few days back on AM3 twice

 

@Pesukarhu Which pins tho?

and

@M.Yurizaki I believe it has labeled SB as standalone, I'll just post pics when I'll go to work tomorrow. ^^

 

Also, don't know why but I "repaired" one PC with that issue by plugging no -5V PSU out, plugging one with working rail, leaving it on for some time and replugging the original -5V one. Dafuq?

[Pesukarhu]

20 hours ago, Zubkover said:

The tester is labeling it as -5V, but even those without this good old white wire are ligthning up the LED for it.

-snip-
 

Also, don't know why but I "repaired" one PC with that issue by plugging no -5V PSU out, plugging one with working rail, leaving it on for some time and replugging the original -5V one. Dafuq?

Wait what? Maybe the -5v led is meant for "all is well" instead of the -5v. Could we have a picture of the tester itself?
 

Perhaps there are issues with the psus and the mobos as well? Maybe it couldn't switch on the bad psu for some reason?

[Zubkover]

12 hours ago, Pesukarhu said:

Wait what? Maybe the -5v led is meant for "all is well" instead of the -5v. Could we have a picture of the tester itself?
 

Perhaps there are issues with the psus and the mobos as well? Maybe it couldn't switch on the bad psu for some reason?

Didn't take a pic cuz I forgot... Well. Derpy me. But that's the one.

But if mobos were bricked it wouldn't turn on afterwards. Also all the rails are present - 12v molex fan working, 5v ligning is fine, and 3.3v in Sata were also fine.

 

I actually test PSUs more with 24v light bulb than multimeter, since in some instances rails have voltage, but cannot provide any meaningful current amount. Thus making this testing more reasurring.