Boot-up weirdness

[Hackworth]

I just finished putting together a general-use system for a friend. It's an
Athlon XP 2400+ running on a DFI AZ30-TL mATX motherboard with 256MB of
"Mushkin Blue" PC2100 memory. The mobo has an AGP slot, but for now the
future recipient of the system just wants to use the integrated graphics.
Also installed are a DVD-ROM/CD-RW combo drive and a 40GB 7200-RPM hard
disk.

Motherboard details are here is anyone is interested:
http://www.dfi.com.tw/Product/xx_product_spec_details_r_us.jsp?PRODUCT_ID=1298&CATEGORY_TYPE=MB

Everything works great and the system handles burn-in and benchmark tests
with no problem... after I manage to boot the system. Whenever I hit the
switch to start the computer, the LEDs blink and the fans spin up, but then
the system just sits there and does nothing, and the monitor does not
receive a signal. If I press the reset switch, the system boots just fine!
This behavior occurs every time I try to start the system.

I can't find anything wrong, although one possible clue is that the -12V
output from the power supply is only -11.37V. If you round off to the tenths
place, that puts it at precisely the outermost edge of the standard 5%
tolerance. Unfortunately, I don't happen to have an spare power supply at
the moment, so I can't test to determine if that's the problem.

Anyone have any other ideas as to what may be causing the boot-up weirdness?

 

[ToolPackinMama]

I can't find anything wrong, although one possible clue is that the -12V
output from the power supply is only -11.37V. If you round off to the tenths
place, that puts it at precisely the outermost edge of the standard 5%
tolerance. Unfortunately, I don't happen to have an spare power supply at
the moment, so I can't test to determine if that's the problem.

Buy one from a local retailer who has a liberal return policy, and try
it. If it solves the problem, keep it.

 

[DaveW]

Sounds like a problem of having an underpowered (or cheap) power supply.

 

[Hackworth]

Sounds like a problem of having an underpowered (or cheap) power supply.

Finally was able to try swapping the power supply with a "known good " unit
(and tested voltage under load w/ digital multimeter to make sure). Same
problem. When I turn the system on the first time, the lights blink and the
fans spin up, but then the machine just sits there and there is no video
output. Pushing the reset button, or powering off and then on again, fixes
the problem and the machine boots and runs fine.

I *have* noticed something, though. The problem seems to occur only when
the system receives no power for more than a few minutes (for example, if I
switch off the UPS on my workbench or simply unplug the system for a bit).
If the UPS stays on, the computer will boot normally on the first try. So...
it seems to me that it's some "feature" of the motherboard where it's always
looking for a voltage on some line. I've never used a DFI motherboard
before so perhaps it's a characteristic of this brand. I've never had this
happen with any other mobo.

Anyone else seen this behavior before?