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Mini-Me
10-25-2006, 02:18 AM
Hi all.
:)

A Dell Dimension 4700 came my way today.
No beep, no video.

Have checked all the obvious things, and have tried removing all the drives, CD-ROM, Floppy...

Tried swapping RAM for known good RAM, still no beep, no video.

There is a ducted cooling fan to cool the CPU ducting air from the outside world into the case. This fan normally runs quietly in the background.

When you fire up the box, this fan tries to go into orbit - makes a hell of a noise, and is spinning as fast as it can.

A quick check with my load tester shows that the 12 and 5 volt rails are healthy, and exactly where they should be.

The CPU power plug(2x black and 2x yellow wires) measures 1.65v when the box is powered.

All this sounds about right to me, so I am thinking that all it can be, is either:

A) The CPU has died or
B) The motherboard has died

Comments would be welcomed.
:)
jlreich
10-25-2006, 10:39 AM
A) The CPU has died or
B) The motherboard has died
It's one or the other. Only way to tell is to put in a known good compatible CPU, or try the CPU in a known good mobo.

How are the caps on the mobo? You might try a new CMOS battery for the heck of it. Or just take the old one out to see if it gets you anywhere.
david eaton
10-25-2006, 12:25 PM
The CPU power plug(2x black and 2x yellow wires) measures 1.65v when the box is powered.

There is the fault! they are 12 volt rails so there is a short somwhere. Unplug them from the M/b, and check the voltage again. If you then get 12 v, remove the processor, and plug thepower plug back in. if the volts go down again, the motherboard it toast.
Mini-Me
10-25-2006, 07:31 PM
I thought that the 4-pin CPU power plug was supposed to be around 1-3v for the CPU core-voltage(depending on CPU). However, you are right - testing a couple of other PC's with these plugs shows a healthy 12v on this plug. I will test the PSU without load on this plug. Thanks to both of you for your comments.
:)
Mini-Me
10-26-2006, 02:21 AM
It would seem then, that this MB has died(and perhaps the CPU too - don't have any other LGA775 boards to test the CPU in)

Removed CPU power plug - 12v.
Removed CPU and replaced CPU power plug - 1.6v

I think it is safe to say, that the motherboard is dead.

Who's with me?
mjc
10-26-2006, 02:33 AM
Good chance of it...
Mini-Me
10-26-2006, 03:24 AM
OK, that's what i'll assume for the moment then.
Thanks everyone.
:)