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Highpower
06-23-2011, 10:06 AM
My daughter has a gaming machine that won't boot up any longer.
Diagnostic LED's on the board (PartyLan, LP nF4 SLI-DR) show that the CPU isn't being recognized. Won't do a POST, no beep codes, nothing.

All the fans run, but after I did voltage checks I found that all the PSU voltages appear to be a bit low. 5V reads 4.4V, 3.3V reads 3.0V, and 12V reads 11.4V. Searching the web, it appears that this particular brand of motherboard is VERY touchy when it comes to PSU's.

It's a 1000 watt supply, but the voltages look suspect to me - and I don't have a clue as to what the lower "limit" is for voltages on these things. :confused:

I've been re-seating connectors, swapping memory, disconnecting drives etc., etc., to no avail. What do you say, those of you "in the know"? :cool:

mike os
06-23-2011, 11:55 AM
PSU readings are fine I would think (assuming they are delivering current too)... these things tend to either work or not ime.... VR's on board sort fluctuations out... I have never had a psu that was spot on, even 'kin expensive ones

possibly CPU is cooked..... but just as likely is mainboard, any lights on the board?

cuemaker
06-23-2011, 12:51 PM
I too agree that the voltages look fine...

This type of thing is the reason why its handy to have a 2nd PSU on hand...

Rule of my thumb, always buy high quality PSU's as they "touch" every componet and good ones are worth every penny....

If it was me, i would pull it apart, reseat the CPU, and then start adding componets one at at time to see if I get beeps to boot up...

macona
06-23-2011, 01:00 PM
Disconnect everything but the mother board from the power supply. Pull all the cards, video, whatever. See if you get a post beep. Check your voltages then.

The voltages dont seem to far from normal. Find another known good power supply and try that.

Benta
06-23-2011, 05:26 PM
Supply voltages are somewhat off.
5 V normally means 4.75...5.25 V
3.3 V normally means 3.0...3.6 V
Your 12 V supply is marginal but OK.

That they are all low seems to imply that either:
1: your meter is not working properly.
2: the supply is being asked to supply too much current somewhere, that would pull all voltages down.
3: the supply is malfunctioning.

Cheers,

Benta.

CCWKen
06-23-2011, 08:01 PM
I don't know where you took the readings but those are all crap for a modern PC power supply. All should be above the rating for each rail but very no more than +/-5%. The 12v rail is borderline failure. I would consider it faulty at the lower edge of 11.4v. If your measurements were taken from the rail leads at the non-boot point, the PS is as good as dead. Your 5v reading is low enough to stop a disk drive from entering ready state.

Highpower
06-23-2011, 09:59 PM
Disconnect everything but the mother board from the power supply. Pull all the cards, video, whatever. See if you get a post beep. Check your voltages then.
Did that yesterday, which is when I took the voltage readings (Fluke 77, BTW) as well. No POST beeps at all.


The voltages dont seem to far from normal. Find another known good power supply and try that.
Did that this afternoon. I dug up a smaller PSU (480 w) just to try powering up the MB to see what it would do. It flew right through the POST without missing a beat - so I guess I have my answer. :)