Re: p4p 800 boot

STEFANO BOSCOLO wrote:
I have changed the power supply with a sure one and no light is not correct.
I have the green led on the board and a correct +5VSB.
I checked the connectors and wires but I have no boot.
What can I control?

Check the Southbridge (ICH5 chip). It doesn't have a heatsink on
it, so you should be able to see the top of it. Does it look
like the picture on this page ? See the "burn mark".

http://www.abxzone.com/forums/intel-chipsets/84122-ideas-burnt-out-ich5r-chip-p4p800-ed.html

If you want to manually start the motherboard, there are two wires on the
main ATX power connector, that can be connected together to start the power
supply. The wires are PS_ON# and COM and the wires are next to one another.
The power supply will run, whenever the two wires are touched together. The
easiest way to access the wires, is to take an ATX extension harness, and scrape
off some insulation there, so you can access the two wires.

But using that method, does defeat certain safety features on the motherboard.
For example, if you manually cause the power supply to be in the "On" state,
there is no way for THERMTRIP to turn off the computer. That is when the
processor overheats. Also, the motherboard may have an AGP_warn circuit, and
the purpose of that circuit is to prevent a 3.3V only video card from being
used in a 1.5V only AGP slot. Manually enabling the power supply, means the
AGP_warn is no longer providing protection either.

So while it is possible to manually start the computer, there is a small
amount of risk that goes with it.

I would start by visually examining the motherboard, for either a
burned Southbridge (ICH5) chip, or look for things like leaking
capacitors.

Also, when you push the power button, do the fans "twitch" or make
a tiny fraction of a rotation ? That is a significant finding as well.
Watch the fans when you push the power button on the front of the
computer case, and see if the fans move a little bit.

Paul



"Paul" <nospam@xxxxxxxxxx> ha scritto nel messaggio news:esqan4$61j$1@xxxxxxxxxxx
STEFANO BOSCOLO wrote:
I had a PC with a p4p 800 SE from a friend.
The computer was working in another house, now we can't have a boot.
I mean no fan and no light.
I have searched on the Internet and it seems to be usual for this MB.
Any idea?
"no fan and no light" = check the power supply.

Make sure the front panel wiring (front power switch)
is still connected to the PANEL header.

Check for the presence of +5VSB on the 20 pin power connector.
You can even do this, by looking for a green LED on the motherboard.
That LED is connected to +5VSB. If the LED is not lit, when the PSU switch
is flipped on, on the back of the computer, then the power supply is
bad, or the power supply is shorting out on the +5VSB.

Paul




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