Friday last disaster struck when the CPU heatsink and fan popped off the CPU unexpectedly (yeh I know it must have been badly fitted now).

The screen went blank but the power supply and internal fans kept running until I shut it down ( 20-30 seconds)

The Heatsink and fan had pendelum'd on its cable, landing on top the AGP card while the PC was running, although testing this card in another PC, it is still working (amazing or what)!!!

Currently the PC wont boot, the case fans and power supply run fine but there is no video bios display and no POST (power on self test) so no beeps to fault find by, and the screen stays a lovely shade of black...grrr !!!

I know the memory is good, so its possible the mobo was damaged by the heastink and fan when it fell, or maybe the CPU?

Question is this - is testing the suspect CPU in my second PC a good or bad idea? If the CPU is bad can it damage my second systems mobo? Likewise if I get a replacement mobo, is it worth trying the CPU in that or could that cause damage too? Would motherboard damage of this type take out the CPU with it or would the 30 secs without heatsink fry the CPU? (Athlon 1200 Thunderbird)

Any ideas please feel free to POST (pardon the pun) :p

Cheers

I would think the most likely scenario is that the CPU is fried.

Athlons run HOT normally, and 20 - 30 seconds without a heatsink..................

so its possible the mobo was damaged by the heastink and fan when it fell, or maybe the CPU?

Yes to both. If the heatsink did any bouncing around it could have landed on top of some of those tiny components on the motherboard and broken them. The ones you have to use a magnifying glass to see well.

If it bounced off the CPU at any time, it could have done the same thing, again a magnifying glass is the only way to really tell if any physical damage was done.

If the CPU is bad can it damage my second systems mobo?

Not likely, every time I've ever tested a bad CPU it did nothing...no video, no beeps, just sit there with the fans spinning. Put a known good CPU in and the boards worked perfect every time. That's not to say it isn't possible for a bad CPU to damage a motherboard, for instance one with bad components that also developed a short circuit, but so far it's always worked fine for me. Just don't test one on a brand new high dollar board straight out of the box...

David and Pete

Thanks for your posts which have stimulated the grey matter a little

I am now toying with the idea of getting a cheap known "working" Duron or similar just to "test" the existing motherboard, as they are freely available quite cheaply on the auction sites and they dont need to be fast and it is possibly the best item to start with. Thanks for the suggestion.

Did I mention when replacing the heatsink I cleaned off the sticky heat pad (or what was left of it) down to the bare copper base and fitted it to the cpu with just a little heat transfer compound of the non silver type. Does the original heat pad provide any form of electrical insulation between cpu and heatsink or not ??

Incidentally talking of chickens and eggs, which came first the CPU or the mobo ???? :confused:

Originally posted by ValeWhale
Does the original heat pad provide any form of electrical insulation between cpu and heatsink or not ??The thermal pad/compound is there to provide a "continuous" medium for heat to transfer from the processor to heatsink...

It appears that most heatsinks are manufactured using an extrusion process and the sinks "chunked" from the continuous length. It also appears that during the cooling process that the sinks cup on the buttom...unfortunately, right in the area where the processor and sink will interface! :(

The copper insert sinks and full copper ones I have used have also been "high-centered" and thanks to mjc, I learned of the lapping process.

http://www.overclockersclub.com/guides/heatsinklappingguide.php

The thermal compounds (e.g., Arctic Silver) are designed to fill in the microscopic voids and also to form an interface between the sink and CPU. I don't know that the thermal pads fill the microscopic voids such as Arctic Silver. Many folks who are overclocking their processors seem to swear by Arctic Silver...

As far as electrical concerns I don't recall reading anything that would be of major concern...however, you might want to check Arctic Silver's web site, as they do also make a ceramic version that has something to do with electrical insulation "issues." Although, I didn't see anything on their site explaining why...

http://www.arcticsilver.com/ceramique.htm