Wife's Computer Won't Start -- Any Ideas?

[jim evans]

My wife's computer won't start. It's a 4 year old homebuilt SOYO
K7VTA Pro and a AMD 1.3 gHz Athlon. It's been running with no
problems for over a year and only a couple of minor problems before
that.

Here's the background. A few days ago she started complaining to me
that her computer was losing time. As I understand it this happened
in big jumps -- like sometimes the clock simply stopped for a while.
Sometimes a long while, like overnight.

She rarely reboots her computer. It runs all the time, so since she
never turns it off it never needs to be reset by the CMOS clock.

Since we were going to be out of town today, she shutdown her computer
last night. When we got home tonight it was hung/frozen in the
shutdown. She tried to turn it off by holding down the power button,
but this didn't work. She then tuned off the power switch on the back
of the computer. After she turned it back on it will not start at
all. The power light does not come on. It's like a lead brick -
*nothing* happens.

Any suggestion on what to look at/try?

-- jim

 

[Shep©]

My wife's computer won't start. It's a 4 year old homebuilt SOYO
K7VTA Pro and a AMD 1.3 gHz Athlon. It's been running with no
problems for over a year and only a couple of minor problems before
that.

Here's the background. A few days ago she started complaining to me
that her computer was losing time. As I understand it this happened
in big jumps -- like sometimes the clock simply stopped for a while.
Sometimes a long while, like overnight.

She rarely reboots her computer. It runs all the time, so since she
never turns it off it never needs to be reset by the CMOS clock.

Since we were going to be out of town today, she shutdown her computer
last night. When we got home tonight it was hung/frozen in the
shutdown. She tried to turn it off by holding down the power button,
but this didn't work. She then tuned off the power switch on the back
of the computer. After she turned it back on it will not start at
all. The power light does not come on. It's like a lead brick -
*nothing* happens.

Any suggestion on what to look at/try?

-- jim

Cheap option 1st.Buy and replace the CMOS battery.Usually a 2032 and
you can get them from Wallmart/Asda

 

[JAD]

PSU would be my guess.
Power strip is bad?
wall outlet on a switch?

 

[jim evans]

Thanks for your reply.

PSU would be my guess.
Power strip is bad?
wall outlet on a switch?

Out of those the only possibility is the PSU. I'm too tired to open
it up tonight I'll do that tomorrow. But the power was still on when
we got home and the computer was frozen in shutdown. Only after she
turned the power switch off and then back on was it dead.

-- jim

 

[jim evans]

Cheap option 1st.Buy and replace the CMOS battery.Usually a 2032 and
you can get them from Wallmart/Asda

-- jim

 

[jim evans]

Thanks for replying.

Cheap option 1st.Buy and replace the CMOS battery.Usually a 2032 and
you can get them from Wallmart/Asda

Can the CMOS battery cause problem when the computer is on all the
time?


-- jim

 

[jbruss]

Thanks for replying.


Can the CMOS battery cause problem when the computer is on all the
time?


-- jim

I agree with the earlier poster to switch the CMOS battery as a first
step. It's cheap and easy. I've had weird things happen when that
battery needs replacing. If that doesn't fix the problem, then the PSU
would be the next most likely source of the problem.

 

[jim evans]

Ok, here's an update.

I replaced the battery, no help.

I removed the power supply and tested it outside the case. The fan
runs and the voltages are all there.

I don't know what the tolerances should be but all the lower voltages
were close to target values, however the +12 is a little less than 11
and the -12 is a little less than 10. All these measurements are made
with the PSU unloaded.

Since the fan doesn't start with the unit installed this is probably a
moot point, but are there voltage test points on a motherboard?

-- jim

 

[JAD]

Ok, here's an update.

I replaced the battery, no help.

Did you clear the CMOS after the replacement? Many times the Bios can be
corrupt after a battery dying/replacement.

 

[Shep©]

Did you clear the CMOS after the replacement? Many times the Bios can be
corrupt after a battery dying/replacement.

And clear the CMOS with the power supply off otherwise the CMOS
re-charge circuit may not let it clear completely :O

Note:The motherboard may be faulty via the CMOS re-charge circuit.No
fix,new board required in that case :/

 

[jim evans]

Did you clear the CMOS after the replacement? Many times the Bios can be
corrupt after a battery dying/replacement.

Well, I hadn't until you mentioned it, but I have now. No change.

-- jim

 

[jim evans]

Note:The motherboard may be faulty via the CMOS re-charge circuit.No
fix,new board required in that case :/

Does the "re-charge circuit" imply it uses a rechargeable battery?
This battery is a primary cell -- it's not rechargeable.

-- jim

 

[Shep©]

Does the "re-charge circuit" imply it uses a rechargeable battery?
This battery is a primary cell -- it's not rechargeable.

-- jim

The 2302 lithium batteries used in PCs can be re-charged to a certain
degree.There is approximately 3v+ DC applied across the battery via a
circuit on the motherboard hence the need to isolate the system from
the mains when clearing the CMOS.
This voltage can be checked with a multi meter with the battery out
and the power supply on.
The voltage can also be checked on a working system in the BIOS or
with software installed in the O/S like,"Speedfan",
http://www.almico.com/speedfan.php

 

[Shep©]

Does the "re-charge circuit" imply it uses a rechargeable battery?
This battery is a primary cell -- it's not rechargeable.

-- jim

The 2032 lithium batteries used in PCs can be re-charged to a certain
degree.There is approximately 3v+ DC applied across the battery via a
circuit on the motherboard hence the need to isolate the system from
the mains when clearing the CMOS.
This voltage can be checked with a multi meter with the battery out
and the power supply on.
The voltage can also be checked on a working system in the BIOS or
with software installed in the O/S like,"Speedfan",
http://www.almico.com/speedfan.php

 

[Rod Speed]

Ok, here's an update.

I replaced the battery, no help.

I removed the power supply and tested it outside the case.
The fan runs and the voltages are all there.

That doesnt prove a lot, it could still be
either the power supply or the motherboard.

I don't know what the tolerances should be

5% on the main rails and 10% on the -12 and -5

but all the lower voltages were close to target
values, however the +12 is a little less than 11

Thats a bit low but you cant measure it unloaded.

and the -12 is a little less than 10.

That too, but it likely isnt used for anything much anyway.

All these measurements are made with the PSU unloaded.

You'd really need to try it with a known good
system for the values to mean anything much.

Since the fan doesn't start with the unit installed this is probably
a moot point, but are there voltage test points on a motherboard?

Yes, but it wont prove anything.

Either the power supply isnt starting because it sees too much load
on one of the rails, or it isnt being told to start by the motherboard,
or it cant actually supply the load because its faulty.

You could try measuring the PS_ON# line on the 20 pin ATX connector
to see if its being told to turn on or not when the power switch is hit.
Green wire.

 

[jim evans]

You could try measuring the PS_ON# line on the 20 pin ATX connector
to see if its being told to turn on or not when the power switch is hit.

What should I see before and after the switch is hit?

-- jim

 

[Rod Speed]

What should I see before and after the switch is hit?

It should be high initially, something of the order of 5V, and pulled low
by the motherboard to turn the power supply on, quite low, below 1V.

Technically its a TTL pullup line, if that means anything to you.

 

[JAD]

What should I see before and after the switch is hit?

-- jim

speaking of switches....i just had one (again) with a stuck switch. I had to push it quite a few
times before it came loose. System powered right up.

 

[jim evans]

It should be high initially, something of the order of 5V, and pulled low
by the motherboard to turn the power supply on, quite low, below 1V.

Technically its a TTL pullup line, if that means anything to you.

OK Here's some new data.

With the mainboard power connector disconnected, two hard drives, a
floppy drive and a CD drive connected the fan comes on and all
voltages look normal.

Under load the +12v reads 11.7v (within specs).

With the power connector plugged in to the MB I checked the PS_ON pin.
It was 5v, and never changed when the power button on the front of the
machine was pushed. I know this button works, so for some reason
closing the power on switch does not cause the PSU to receive the
power on signal/state.




-- jim

 

[jim evans]

You could try measuring the PS_ON# line on the 20 pin ATX connector
to see if its being told to turn on or not when the power switch is hit.

Thank you very much for this suggestion. I think it is going to lead
to the answer. Please see my other post explaining the results of
this test.

-- jim