Computer won't start up

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I have a computer that's acting up. When I plug it in, the power
supply fan and the main vent fan both start and two lights next to
where the network cable plugs in light up. After about a second, the
two lights go off and the fans power down. After a couple of seconds,
the fans come to a stop and then the whole cycle repeats. It continues
repeating this activity until I physically un-plug the power cord. If
I re-connect the power cord, it immediately starts cycling through
this same pattern again.

I thought probably the power supply had gone bad (the computer is just
under a year old). So, I bought a new one and installed it. It made
absolutely no difference. It still behaves exactly the same.

Any one have any thoughts as to what might be wrong with this thing?

Re: Computer won't start up

Martin wrote:
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Physically inspect your motherboard for domed or vented capacitors.
There are pictures of what those look like on the web if you're
unfamiliar with the term.  Also look to seem if there's some sort of
spill or debris that could be shorting the board.

While you're looking, find the pins where the power switch plugs into
the motherboard.  Disconnect the power switch, and plug it in.  It's
probably not the case, but a shorted power switch might produced the
effect you're seeing.

If it's still a mystery, reduce your system to a minimum state:

1) Pull all expansion cards, except for video if you need it.  (If you
have onboard video, use that.)

2) Disconnect all floppy, hard and optical drives by pulling the cables
at the motherboard side.  Disconnect those drives from your power supply
as well.

3) If you have more than one memory module, determine from your
motherboard if you can run with only one of them.  Swap in different
ones to try to account for a bad module.  Better yet, put in some known
good memory that is compatible with your board.

4) Disconnect all firewire, USB and PS/2 peripherals.

If you can get your BIOS to start, you can add in a small set of
components to go for a POST and OS boot: keyboard, mouse, boot drive.
If you can continue from there, add it components, a few at a time,
until you find the culprit.

If it's not the power switch, though, I tend to suspect your motherboard
is bad.

Re: Computer won't start up


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Grinder / kony -

Thank you both for the excellent responses.

After trying the things you suggested, Grinder (and not having any
luck), I called tech support - it's a Lenovo / IBM unit. It's still
under warranty so they're going to replace the mother board.

Re: Computer won't start up

On Mon, 21 Apr 2008 11:41:00 -0700, Martin

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Leave battery out with AC disconnected - for 10 minutes,
then use the clear CMOS jumper and reinstall battery - check
it for proper voltage and replace if voltage is low.

Disconnect the power and reset buttons, all the case
connections actually, and use a metal object like a
screwdriver tip to short the PS-On pin to adjacent ground to
turn on.  Do this even if it is power-cycling on and off
right after AC is plugged in.  Be sure you have the correct
two pins and hold that contact with the metal object for
more than 4 seconds.

You failed to detail what motherboard, what power supply(s).
Also be sure you have all other external peripherals
disconnected like keyboard, mouse, usb devices.  Lastly
disconnect all but bare essentials out of the case on a
non-conductive (Not anti-static mat or bag) surface,
installing or leaving installed only CPU, 1 memory module,
video  and clear CMOS with AC disconnected again).  Retry
and if it doesn't work, call it dead unless you have a 3rd
PSU you want to try or another compatible system to check
the remaining (video, memory, CPU) parts to see if they work

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