Ron said:
I went away for all of last week and shut down my pc in the usual way
and also switched of the power at the mains as well. On my return
when I switched it back on, it starts up as soon as I turn the mains
on at the wall socket. The power pack starts, the fans on the power
pack, cpu and motherboard run, the keyboard and mouse light up, the
dvd/cd drives light up but it does nothing else. No beep, no hard
drives, no signal to the monitor, no response from the power button. I
also can’t shut it down at all other than by the mains on off switch.
I have removed every lead and plugin component from the motherboard,
including the bios battery, and one by one reconnected each trying to
power up each time but I just get the same thing.
I seem to be getting power to the motherboard Gigabyte GA-81PE1000
with P4 3.0Ghz proccessor as the fans on the board run but I am now
out of ideas.
2mb ram
Windows XP pro
Homebuilt pc in Lian Li tower case 7 years old
This is just a hunch...
I think your Southbridge is blown. The Intel ICH5/ICH5R has a problem
with static electricity. At least, a lot of failures correlate with
handling USB devices on the computer front panel USB ports. But there
also seem to be a couple failures, where the problem may be related
to +5VSB. Intel has never acknowledged the problem, but Gigabyte did.
This is Gigabyte's warning.
http://tw2005.giga-byte.com/Motherboard/Support/FAQ/FAQ_456.htm
This page says you have ICH5. Likely a lot of other members of
the same motherboard family, use that chip. The ICH5 usually has
no heatsink on it, making visual inspection easy to do.
http://www.gigabyte.com.tw/Products...rboard&ProductID=1647&ProductName=GA-8IPE1000
The ICH5 can fail two ways. It can burn, with a mark in the center.
This picture, is one of the first used widely as an example.
(This ICH5 won't be booting any more... R.I.P.)
http://onfinite.com/libraries/179057/2ea.jpg
Or it can fail silently, and all that happens in a "minor" failure,
is all the USB ports die, but the board can still be booted. In
the minor failure case, you can install a PCI USB2 card and continue
on your way.
But your symptoms, indicate the ICH5 is currently under stress. The
Southbridge has multiple power rails, and at least one of the "wells"
is sensitive to abnormal loading on things like IDE cables. Perhaps a
USB port failure, would also upset the power control logic, and cause
the computer to switch on immediately. The fact it won't boot, is
indicative of a major Southbridge failure. If the ICH5 burns, it
won't boot any more.
The failure type seems similar to "latchup failure". That is where
a CMOS totem pole, turns into an SCR (silicon controlled rectifier),
and conducts current directly from rail to rail. That causes the
chip to get burning hot. If the bond wires burn out first, you
have a "minor" failure type, and the USB loses its power source
forever. If the bond wires hold on for half a minute, then the
rest of the chip fries, and "she's done".
http://en.wikipedia.org/wiki/Latchup
Anyway, take the side off the computer, get a strong light,
and have a look. It should be relatively easy to find the Southbridge.
In this example, it has a couple red SATA ports right next to it.
You can see there is no burn mark on the ICH5 here
http://www.gigabyte.com.tw/FileList/Image/motherboard_productimage_ga-8ipe1000(rev1.x)_big.jpg
By the way, I've read about 30 reports of this problem, for more than
one brand of motherboard. One guy set a record, by having something
like five motherboards fail that way. Back in its day, there was
an epidemic of these. One guy, even had a new ICH5 soldered to
his motherboard, as it was still covered under warranty. Even if
there was a hidden warranty for this, it's probably expired by now.
You can always contact Gigabyte and see what they say, if the failure
is the burn mark kind.
Good luck,
Paul
