motherboard beeps like ambulance (more complex problem) - help appreciated!

[bj]

Good morning,

I had my PC repaired recently; the guy who came replaced the motherboard and
the graphics card. Afterwards, I found that he had put in a weaker processor
(AMD Athlon 2000) than I had had before (2200), so I wanted to replace that.
I detached the processor fan and replaced the processor.

Now, when I turn the PC on, for half a second a green diod lights up and the
fans go on, then the motherboards starts emitting pulse beeps like an
ambulance siren (eeeeooooeeeeooooeeeeoooo...) and everything (but the beeps
and the red diod) stops. Does anyone have an idea what the problem may be,
please? This persists also when I switch back to the old processor.

I had checked forums and found that this signal is typically emitted when
the processor temperature is too high. The old one that I removed had some
old paste on it, but the new one does not heat up in the half-second when
the PC seems to be working.
I plugged in the CPU fan and radiator (only did not click it on yet as it's
rather difficult, it requiring detaching the whole motherboard, but this
should not matter, should it?);
I switched the CMOS (?) jumper back and forth and even removed the battery
for 1 minute;
I removed and put the memory back in, checking the connections;
No capacitor seems to be swollen;
Apart from replacing the processor I didn't seem to be do anything.

Motherboard: Abit HF7; processor: AMD Athlon 2200

Could anyone suggest a solution, please? I have no more money for another
repair, and this is rather exasperating...
Loads of thanks in advance!

-bj

 

[Paul]

Just a couple of possibilities:

Well down your notes you say "I plugged in the CPU fan and radiator (only
did not click it on". If you've been running the CPU without its heatsink
firmly fitted then you've almost certainly killed the processor(s).

The other possibility is that you've damaged a thermistor (temperature
sensor) on the motherboard. I don't know your particular MB, but many have a
small thermistor on the MB centred immediately under the CPU socket.

Agreed. Fitting the heatsink/fan assembly is crucial.

I can see a picture of the Abit NF7 version 2.0 here, and there
is an eight pin chip located within the processor socket. That could
be an overheat detector. I had a similar concept on my A7N8X-E Deluxe,
where a chip was placed on the motherboard, to monitor the diode temperature.

http://www.xbitlabs.com/articles/mainboards/display/abit-nf7_2.html

What that does, is take measurements from the diode anode and cathode,
right on the CPU die of the Athlon processor. If the voltage developed
across the diode passes a certain threshold, the eight pin chip has a
"shutoff" signal that can be tied into the power supply PS_ON# logic.
And that would be why the motherboard is switching off. This datasheet,
is an example of a chip used for the function. Attansic makes a similar
one, but without SMBUS connections. When a chip like this has SMBUS
connections, you can also read out the temperature with Speedfan or
a similar utility.

http://www.winbond-usa.com/products/winbond_products/pdfs/PCIC/W83L785TS-S.pdf

Properly fitting the heatsink/fan assembly, is all that is required
at this point. That means cleaning off the old paste, applying a
bit of fresh paste, then "clicking down" the heatsink assembly.
There could be a metal clip, with either one-hole or three-hole
pattern on the end, which fits onto plastic tabs on the side of the
socket.

(Instructions for applying paste)

http://www.arcticsilver.com/pdf/appmeth/amd/ss/AMD_app_method_surface_spread_v1.1.pdf

The only danger, while fitting the metal clip, is having your
tool slide off the clip and hit the motherboard. Some clips
could be addressed with a hex driver, rather than a flat blade
screwdriver, and the hex driver wouldn't slide off as easily,
reducing the risk of striking the board. (The end of the hex driver,
fits over a raised metal tab on the clip, which is why the
hex driver won't slide off.) Even so, in the NF7
in the picture above, there are protective strips shown on
either side of the socket, in an attempt to protect the
motherboard from damage.

(This is the dangerous part - having the screwdriver blade slip off.
In some cases, a hex screwdriver will fit the raised metal bit,
and give some lateral control while fitting the clip.)

http://www.crazypc.com/images/articles/heatsink/fronthookscrewdriversmall.jpg

( from http://www.crazypc.com/articles/hsfinstall.htm )

On my Nforce2 motherboard, I used a Zalman 7000 cooler, and
that one screws to the motherboard, rather than using clips.
That avoids some of the dangers of the tab kind.

If the motherboard still won't POST properly, then perhaps
the new processor IS damaged, and it is time to put the
old (2000) one back.

To make the "eeeeooooeeeeooooeeeeoooo..." sound, takes
execution of some processor code, so I suspect the processor
is still alive. If the computer case speaker was
completely silent, then you'd be in trouble.

Paul