Computer Won't turn on

[Jack Bruss]

My Dad has a problem with his computer. It won't turn on - that is the hard
drive doesn't spin, the fan doesn't go on, and the power light doesn't go
on. My Dad said that a few weeks ago it would not turn off, but as of about
1 week ago it won't turn on. We took the case off and played with the
switch, but still no go. I've checked the power cord - it's ok. I'm
wondering if it's the power supply or the switch. What's a good way to
diagnose a problem there? Is there something else it could be? We replaced
the battery.

Thanks,

Jack

 

[Strontium]

Short the pins (where the power switch wire connects), on the motherboard,
with a screwdriver to determine if it's the switch. You might also need to
disconnect all of the components from the PSU and add them back, one by one.
There was another lengthy post on testing the PSU, as well.


-
Jack Bruss stood up, at show-n-tell, and said:

 

[Jack Bruss]

I've ruled out the switch as the problem by shorting the pins as you
suggested, and also by getting continuity across the switch wires when I
press the switch button.

I found the thread on testing PSUs, and I guess I'll try to do that, but
this is a 4 year old computer with an AMD 350 processor, and I imagine, a
low wattage psu. I would think I could get a replacement psu pretty cheap.

Anyway, any other thoughts before I go that route?

Thanks

Jack

 

[Jack Bruss]

Well, the voltage on the pins of the 20 pin connector are as they are
supposed to be, but what I found is when I push the 20 pin connector around
in it's socket on the mother board, I can get the computer to turn on.
Also, I now can't turn it off with the switch, but I can turn it off by
pushing the connector around in it's socket.

So I guess this means that I've got some kind of loose connection between
either the socket and the mb, or between the connector and the socket, or
between the connector and the wires.

Any thoughts on how to fix this?

Thanks,

Jack

 

[w_tom]

Suspect various reasons for failure, or go right after the
problem with vengeance. Anyone who does computer repairs
(responsibly) has the so essential (and so inexpensive) 3.5
digit multimeter. Don't remove anything. Do not wildly
replace components. Simply and first measure voltage on
connector from power supply to motherboard.

Motherboard controls power supply. First measure +5VSB so
that motherboard control electronics can work: Measure
voltage between purple wire and any black wire. If +5 volts
exists, then measure voltage between green wire and any black
wire. This will something less than +5V when power is off and
will drop to near 0 volts when power switch is pressed. 0
volts on green wire means power supply should turn on.

If these voltage exist, then voltage on other wires is
monitored when power switch is first pressed to power up
machine. Any voltage that does not make an effort may be
shorted by system. Power supplies power up all essential
voltages. Then checks those voltages. If one voltage is not
stable, then power supply automatically turns off all
voltages. That one voltage that does not even try to rise may
be shorted. Chart for voltages is found in:
http://www.hardwaresite.net/faqpowersupply.html

Pin 20 is +5 volts. If that pin was defective, then other
wires would complete the same connection. However if one pin
is defective, then multimeter would detect a voltage across
that intermittent connector. Again, no reason to wildly
replace things. That meter will detect broken connections,
open wires, and insufficient power supply voltages.

 

[Jack Bruss]

I hadn't realized it, but we had a spare power supply laying around here, so
I plugged it in, and the computer seems to work now. At least I can turn it
on and off. I was able to mount the spare ps to the case, so I think I'm
all set now.

Thanks to all who left advice.

Jack