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From: Justin Shifflett on 12 Jul 2010 11:46
Adding that the light on the PSU unit is solid green. Stays green a
little while after unhooking the power.

It's a Bestec ATX-250-12z

From: Paul on 12 Jul 2010 14:16
Justin Shifflett wrote:
> Adding that the light on the PSU unit is solid green. Stays green a
> little while after unhooking the power.
>
> It's a Bestec ATX-250-12z
>

Uh oh!

The history is, the Bestec ATX-250, was the brand of supply that
would fail "overvoltage" and blow other components like the motherboard
and hard drive. The bad supplies might have been ATX250-12e , while
your one has "z" on the end and might be a different design.

Would Bestec have learned their lesson, and designed a better power
supply ? I can't answer that. I don't know enough about the company.
With the grief they've caused, I wonder why any manufacturer would
continue to do business with them. Your computer is relatively new,
compared to the Emachines and other computers that 12e supply damaged.

One test you can try, is slave the hard drive from the non-functional
computer, to another computer, and see whether the hard drive can be
read or not. (Testing the hard drive, is to see if the power supply
has ruined stuff on you. If the hard drive is good, then that
increases the odds you can repair the machine at moderate cost.)

The hard drive has two transient suppressors, on the +5V and +12V
rails. They're not designed to protect against power supply failures.
They are present to protect the hard drive against overshoot when
the power goes off. At least one poster figured this all out, and
provided me with an education. He found burned components on his
hard drive, traced down the numbers, and then I read up on them.
If you had a sustained overvoltage event, and the hard drive
no longer responded, the burned state of those one or two
components, near where the power comes into the drive on the
drive controller board, would provide some confirmation there
was an overvoltage failure. A high current flows through the
transient suppressor, if the ATX 12V drive voltage goes to 15V.
Because the high voltage is not a transient, but a steady
condition, it gives the components time to burn up.

You could use a multimeter and verify the power supply voltages.
At this point, it probably doesn't make any difference any more,
as to how many more times you turn on the power supply. If it
has damaged the computer, it probably can't do any additional damage.

Modern power supplies have features such as

1) Overvoltage protection. Supply shuts off, if, for example, the
3.3V rail rises to 4.7V. That can also help in situations, where
one rail of the supply, gets shorted to another rail.

2) Overcurrent protection. Sometimes used on multiple output 12V supplies,
limiting current flow on each so-called "separate" rail. I suppose
that leads to a shutdown as well.

3) Overtemperature protection. The power supply may have a thermistor
on one of the internal heatsinks, to detect an effective cooling
failure, or cover the case where the power supply is delivering
too much total power for its own good.

You can save a few pennies on a power supply design, by removing that
stuff. Then, on a failure, there is a lot more collateral damage.

At this point, you can change the supply, but the symptoms might not
change, due to the damage it did to the motherboard. In terms of
"swap order", I'd still do the power supply first. Since the original
is a 250W, you should be able to use just about any ATX compatible
supply you have near you, for a quick test. But if the motherboard
and/or hard drive got damaged, the symptoms might not change
with the new supply.

And I don't see any of those motherboards on Ebay. The main reason
for wanting the same motherboard, is so the royalty OEM OS install,
will continue to restore OK to the machine. You can also reinstall
from a regular Windows CD, but the CD type has to match the original
install, so that the license key on the machine will work.

I sure hope there is some warranty time left on the computer. If it was
only a one year warranty, chances are you're screwed. Talk to HP
anyway, and see what they say.

The mouse light may be coming on, because it is running from +5VSB
from the power supply. Perhaps that rail is OK, as +5VSB comes from
a separate part of the supply.

Knowing it's a Bestec, doesn't change the repair procedure that
much, except to suggest one additional test, to check for
collateral damage. The hard drive and optical drive could be
ruined, if +5V or +12V go higher than normal.

Paul
From: Justin Shifflett on 12 Jul 2010 19:24
I went ahead and tested another PSU. The fans started, but nothing
else. So I'm guessing it's likely the motherboard now. Hopefully
replacing it with an identical one will prevent data loss.

From: Paul on 12 Jul 2010 22:28
Justin Shifflett wrote:
> I went ahead and tested another PSU. The fans started, but nothing
> else. So I'm guessing it's likely the motherboard now. Hopefully
> replacing it with an identical one will prevent data loss.
>

I'm curious about the hard drive. Test it on another computer
and see if it survived.

Paul
From: Jeff Strickland on 13 Jul 2010 11:32
I can't tell what the trouble is, but one thing that should be on your list
is a failed Power Supply.

You didn't say, but the keyboard could be a PS2 and the Mouse could be a
USB, and this could explain why there is power to the light on the mouse,
but no response from the keyboard. Of course,l the keyboard could be USB and
the mouse PS2, and the same symptoms could occur.

I don't know what other loads are driven by the voltage that goes to the the
different circuits, But the USB is usually about 5v, so anything that runs
from 5v would not work, which is lots of stuff.

You can buy a power supply for under 50 dollars and get greater capacity
than you have now.

You could test the power supply with a volt meter, or maybe by unplugging
all but the essential loads. If your machine worked until you added the most
recent accessory, then it's possible that the new accessory overloaded the
power supply. Sometimes you can unplug the overload and get the power supply
back. If this is the case with your problem, then a new power supply with
more power capability is in your future.





"Justin Shifflett" <justinshifflett(a)gmail.com> wrote in message
news:ade603b3-1712-450e-abc6-2aa096c1eb14(a)z10g2000yqb.googlegroups.com...
>I was told I should post here.
>
> I don't want to have to replace the motherboard if I don't have to.
> But I think I do.
>
> My PC will turn on. The fans will run. But the PC won't detect the
> keyboard. It will however detect the mouse (it's optical, and glows
> red). Nothing will happen on the monitor, and the monitor light will
> turn yellow like nothing is on-- but the monitor works fine, as it's
> being used on the current PC I'm on.
>
> I called HP (The company that made my computer). They went through
> the steps with me-- getting Static Electricity out of the system,
> reseating the Ram, listening for beeps (there weren't any as far as I
> could tell.) ANd they said they thought it was a Motherboard issue.
>
> I don't know what else to do. I've tried just about everything I can
> think of. It's weird how the mouse will be read, but nothing else
> will. I dont' know if it's the motherboard, the CPU, or what.
>
> Any tips?


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