Re: 2 PCs not starting up properly nor shutting down

I'm confused why you are disconnecting power supply from
motherboard - or disconnecting anything. Disconnecting means more
possible damage, consumes time, and makes numbers less useful.
Measure both before and as the power switch is pressed - regardless of
whether computer and fan appears to start.

Hopefully the AC power cord was disconnected from wall receptacle
before disconnecting anything. Otherwise more damage may have been
created. Another reason why repair starts by disconnecting or
removing anything.

Purple wire is OK - the only useful number being when supply was
connected to motherboard.

Green wire at 0.78 volts is too high - a defect. But apparenly the
power supply is turning on anyway as indicated by voltages on red,
orange, and yellow wires? (An example of how a defective power supply
may still power on a computer.)

Gray wire voltage is OK when power supply is on. However not
provided is the same number before power switch is pressed and what
happens as power switch is pressed. A delay should have been noticed
between power on and voltage rising about 2.4 volts. Moving on.

Important are what those numbers do and do not do when power switch
is pressed. Does not matter if computer does nothing when swtich is
pressed. Important was what each wire does before and as switch is
pressed. For example - purple wire was at 5.1 volts before switch was
pressed. What was it as switch was pressed?

If power supply does nothing when switch is pressed, then where did
the 3.43, 5.15, and 12.1 come from? Were these when the power supply
was connected to motherboard and only when and after power switch was
pressed? I am a little concerned with the 3.3 volt number - it is
border line high. Not excessive, but very close to exceeding
maximum. Would not cause a computer failure, but a useful fact that
may or may not be useful with other information. Currently only a
concern and not a problem.

Assuming these numbers were all when everything (including video
card and disk drive) were connected, then the power supply is good
except for the green wire. Power supply was telling computer to power
on. Except for green wire, the power supply system is OK.

That green wire problem could be either a motherboard defect or a
power supply defect. Another test later can determine which is
marginal (defective). This defect could cause a system to rarely
(intermittently) shutoff for no apparent reason.

Before moving on, first confirm for me the assumptions I made here
to claim the power supply as (mostly) good.

On Nov 16, 7:39 pm, Erik <E...@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
My apologies for the late reply; I have the most "fantastic" work hours...
But today I had some time off.

I managed to test the drives of the first computer that failed, today; and
they all seem to work fine. I connected those to my own PC, one by one, did
some testing (with HD tune, to give them a good workout, and played a DVD in
the optical drive). No problems at all. (I just realized I forgot to test the
disk drive...)

Other hardware in the PC that failed first were an AGP card, and a wireless
network card. The wireless card was installed in the backup PC a few days
ago, and works great. The AGP card, unfortunately, I can't test. The backup
PC has no AGP slot, and my own PC has a PCIe slot...

I have not managed to do anything on the backup PC; my wife needed it for
her online classes today.

OK, I did the voltage test as described in your article, on the first PC.

I disconnected the ATX connector from the MB for the first part of the test;
because the CPU heatsink obscures part of it, and is hard to reach with the
probes.

The purple wire measures 5.20 V. After hooking up the ATX connector to the
MB the voltage goes down to about 5.10 V.

The green wire measures 4.66 V. (again, before being plugged into the MB).
After I plug it in to the MB, and turning on the PSU's switch, it goes to
0.78 V.

The gray wire measures 5.15 V. ("well above 2.4 V", as you say in your other
message, but maybe too high?)

I measured 3.43 V, 5.15 V and 12.10 V on the orange, red and yellow wires,
respectively.

I hope you can tell me a little more from these voltages. Please remember
that I couldn't perform the test exactly as you describe; because pressing
the power button on this PC doesn't do anything at all.

If it is significant: I noticed that the power supply's fan does not come on
when the ATX connector is not hooked up to the MB (even though the PSU is
switched on in the back).

Does this mean anything to you?
.

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