820-2850 cpu is running hot sometimes, fan full speed

[Dozer]

hi friends.

this mainboard is running good but sometimes the fan is spinning full speed.

in asd no errors.

sometimes, in asd, or in osx the fan beginns to running very fast. took a look at the temperatures cpu temps are over 100C.
at first i thought a defect in the sensors but touched the mainboard its realy very hot under the cpu.

i tryed new thermal paste and another heatpipe already but nothing.

sometimes its cooling down to 66-70C, sometimes it runs a time without problems

another time it starts to going hot after minutes.

any idea where to look what problem that could be?

 

[dukefawks]

Could be many things. Measure Vcore voltage and compare if there is any difference when it gets hot. Download CPUTest and let it run and see what the temps do.

 

[Dozer]

ok, thanks for quick help, I will do that and report back. another time eater board, so it will take a little...

 

[Gurmon]

I had one of these units recently with a bad heatsink. check the copper surface to see it hasn't sunk in a little.