Re: PC Power supply

In article <2FoQj.7$1m3.5@trndny02>, jamessweet@xxxxxxxxxxx says...


"Charlie Bress" <left@xxxxxxxxxxxxx> wrote in message
news:LaWdnZ7oG-3cjo_VnZ2dnUVZ_tWtnZ2d@xxxxxxxxxxxxxx
My son has an E-Machine T3828 that will not power up. Unfortunately he is
around 100 miles away so I do not have more information. There were no
changes made to the PC that might have caused this.
At first glance it is easy to blame the P/S itself, but a new replacement
did not help.

A detail: He reports that with either supply there is a single LED on the
M/B that lights up. What controls this light?
On either P/S there is no other sign of life. No fans turn on.

What are the likely causes?

I have considered some. The power switch may have failed. Or the
mechanical
link from the front panel to the switch.

IIRC there is a pin on the M/B-P/S connector that provides an input to the
supply so that the supply turns on.. Is that a set level? What controls
it?

I am considering having him drive down with it. I can repair electronic
devices, but I have never come across this situation.

Is there a likelihood that the fault is in the M/B?


Thanks,

Charlie



The light is simply wired to the standby output of the PSU.

I've seen bad motherboards cause this, could also be the power button or the
wiring between that and the motherboard. The other time I saw this the
graphics card was not fully inserted in the slot.



I have seen that symptom caused by bad RAM, overclocking the CPU,
corrupt BIOS. Sometimes a bad PSU will pop the MB's regulation system
too. You will find that most E-machines are considered disposable due to
the their low cost. Make sure the replacement PSU is pin compatible with
the old one. Just because the connectors are the same, doesn't mean the
the pins are carrying the same voltages.

I would remove all cards (not RAM) so the system is bare bones, and see
if it generates a no video card error. At least you know the system is
doing POST (Pre Operating System Tests) at that point. You can also try
to move the RAM to a different slot, as failure with ram in the first 64
megs or so will cause the system to refuse to do POST. Sometimes moving
it will clean flaky contacts. The ram should run in any slot, providing
it meets the specs for that slot. Some MBs have 2 different kinds of
slots on the same board. Of course if the ram is bad, then it may not
boot at all.

I had one guy complain that the system he built would come on then
immediately go off, so it *had* to be defective cpu or the like. It
turned out that he had not mounted the CPU heatsink and fan properly,
and it was up on one side. The cpu heated up very quickly, and shut the
system down to protect itself. Gotta love those AMD CPU safeguards. Once
the problem was rectified, the computer ran like a charm, and he is
still using it today.

- Tim -
.