Re: 2 PCs not starting up properly nor shutting down

Hello again.

First, let me say that it seems we're not exactly on the same page anymore.
For clarification: when I said that the power supply is off (and consequently
the PC), I meant that I turned it off with the switch on the power supply.
Since that is rigged to the mains there are absolutely no voltages going to
the PC.

Since CPU and case fans, drives etc. come on as soon as I flick that mains
switch, when the cables are hooked up to the MB, the only way I can test the
"before pressing case power switch" voltages is by disconnecting the cables
from the MB, because pressing the case's ON/OFF button doesn't do a thing. I
gave you those readings in my first voltage test; here they are again:

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. (when it's plugged into the MB it goes to
0.78 V.)
The gray wire measures 5.15 V. (and reads the same after I plug it in to the
MB)

Before power switch is pressed, that green wire will measure
something above 2 volts. When power switch is pressed, the green wire
will drop to near zero and gray wire will rise above 2.4 volts.

Again, pressing the case's power switch does nothing. System gets powered
right away after AC is applied.

Then
motherboard's BIOS (program) should execute. It will find no memory
and beep an error code on the speaker (or beeper soldered to
motherboard).

No beeps heard...

We knew power switch and power supply system are functional (even
with a marginal green wire voltage) from previous and current
measurements. If speaker does not beep, then suspect only motherboard
or CPU. CPUs are almost never damaged since so many motherboard
functions protect it. CPU damage typically means motherboard caused
its failure. Primary suspect identified.

In other words: the motherboard would be defective?

If speaker does beep, then motherboard and CPU are functional.
Suspects are those other peripherals - a most likely suspect being the
video controller.

Remove AC power cord. Install only the video controller. Reconnect
power cord. Perform same test. Does speaker still beep? If not,
primary suspect identified. If yes, repeat for other peripherals (but
no memory) until something causes that speaker to not beep.

I skipped the last 2 paragraphs, as they don't seem to apply (I get no beeps
at all).

Any other suggestions?

Thanks,

Erik

On Nov 17, 3:47 pm, Erik <E...@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
OK, so here are some more numbers. Power supply (including 4 pin 12 V
connector) hooked up to MB, graphics card and 1 drive installed.

Power supply switch in ON position. Power supply fan comes on, CPU fan comes
on, graphics card fan comes on, HD starts spinning.

Without touching the case's power switch:

Purple: 5.17 V
Green: 0.78 V
Gray: 5.15 V
Orange: 3.43 V
Red: 5.15 V
Yellow: 12.10 V

Pressing the case's power switch:

Purple: 5.17 V
Green: 0.78 V
Gray: 5.15 V
Orange: 3.43 V
Red: 5.15 V
Yellow: 12.10 V

As you can see, the voltages are the same.

I checked the operation of the case's power switch with the Ohm meter, and
the switch is OK. The same for the reset switch.

In the message that you referred to in your first reply, you say that the
voltage on the green wire should be "well below 0.8 V when the power switch
is pressed". I take it my 0.78 V is not low enough then?

I don't have much more time to test anything today; as I go to work in less
than an hour. However, your thoughts would be very much appreciated (and I
will read them today at work); so please don't hesitate to send me any other
tips about things that I can test; and I'll get to that tomorrow.

.

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