out of spec rails

[Achelon]

Hi,

I have an AK77-600 Max with out of spec voltage rails. This mobo was recapped a while back. Both before and after the recap the 5v rail was pretty low but now things are quite bad. The pc hangs (especially when lots of high current drawing USB devices are attached such as ipod + wifi dongle).

Here are what the rails look like now:
Vcore(V): 1.62
+3.3V: 3.25
+5V: 4.73
+12V:12.43
-12V: -11.93
-5V: -5.79
5VSB(V): 4.80

Under high current draw 5v rail seems to experience a sag in voltage, sometimes to 4.70v and below. A number of symptoms are evident such as Ipod having difficulty charging. I replaced the 550w Xpower PSU with a Powwa 600W but the voltages on the rails is unchanged. How do I go about diagnosing this problem? I cannot accept 2 PSUs are identically bad.

Regards,
Achelon

[kikkoman]

Re: out of spec rails

the AK77-600 draws most current from the 5V and 3.3v rails (instead of 12v for newer boards, >P4 era) and those PSUs provide most of the juice on the 12v rails.
----> bad combination.
you should look out for an older PSU that provides high 5v+3.3v current. there are pretty cheap yet good units available, you won't need more than 300W for a moderate system anyway.

there's also the possibility that the push-pull bias between 5 and 12v can be adjusted in those PSUs of yours but i don't know how solid they are----> don't know if they are stable enough for that shift of load.
getting an older PSU is the way to go.

EDIT: the X-Power is a Powmax. get rid of it as fast as you can.
the Powwa isn't much better, probably.

[Achelon]

Re: out of spec rails

Hi,

Thanks for your input. I still feel suspicious tho that 2 very different PSU's give unchanged voltage ratings on the mobo. I forgot to mention that I ran the mobo with badcaps in the filter bank in the CPU VRM for an extended period of time before I fixed them, is out of spec rails associated with any problems that could result from this (eg damaged mosfets?).

Regards,
Achelon

[370forlife]

Re: out of spec rails

Two terrible psu's, thats one problem.

[kc8adu]

Re: out of spec rails

are you measuring with a dvm or some sort of monitoring util?
and it seems you do have 2 crappy psu's.
at least that cannot take the heavy load that board presents to +5.
the tipoff is the +12 running a bit high.
just looking at the pic of the powwa shows input stuff showing through the case but it just has that cheap look about it.
get a unit from before the p4 era and try it.