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View Full Version : Promblem with mobo / PSU combo

Hagar
06-06-2007, 03:12 PM
I have an Epox 8KDA / Sempron 3400 that has worked very well for about a year. Now I need to move it to another chassis, but there it would not power on.
So I placed the mobo on the table. Everything but the CPU was removed. When I press the power button it starts for an instant but then shuts off immediately.
It still works with the original PSU, a NorthQ. But it fails with the new Chieftec, and it also fails with another Chieftec (labled Delta). Both these PSUs work OK with other mobos.
If I remove the CPU the PSU will start.
After one such failed start there is absolutely no reaction on further attempts until it is reset with a pulling the mains plug. I found the same happens when I pull the 20-pin ATX plug, which means it is the mobo that needs a reset (the standby circuit, I assume).
I have done a CMOS reset several times.

So, any idea why my mobo does not work with a Chieftec PSU?
ski
06-07-2007, 09:54 AM
Does the MB work in the original case?
Hagar
06-07-2007, 05:31 PM
Well, yes. But as I said, the case is taken out of the equation, to narrow down the problem to only the PSU and the motherboard.
ski
06-08-2007, 09:41 AM
My point was to go back to square 1, and reinstall the MB in the original case where it had previously worked. If the MB does not work there, then the it may be bad.
Hagar
06-08-2007, 12:00 PM
As I wrote, "It still works with the original PSU". So I repeat, the MB works OK with the NorthQ PSU.

Today I updated the BIOS to the latest version. Then I tried the Chieftec PSU and it was working! But next restart it was back to the same problem.
ski
06-09-2007, 11:05 AM
My brain was in the non-absorbent mode. Sorry 'bout that.
azzey
06-13-2007, 02:32 AM
You have the CPU fan mounted and plugged in, right? Lots of motherboards won't boot without it.

How many pins does the motherboard have? What about the PSU?
Hagar
06-13-2007, 03:20 AM
The fan is OK. Its a 20-pin MB.

I measured the PS_ON signal (ATX pin 14), it goes high after 50 mS. So it is the MB that turns off the PSU.
The Chieftec PSU was actually working for a while yesterday, so whatever the problem is, it is marginal.