Laptop only works without heatsink - HP ZBook 15 G1

[mr.Data]

I have a ZBook 15 G1 with a very strange problem.

When I mount a heatsink the laptop is sometimes booting but mostly black screen.
When I unmount the heatsink it works until the heat makes the laptop shut down with build in protection.

When the laptop doesn't boot the capslock light blinks 1 times which indicated the CPU.

Tried different CPUs but the same problem keeps occuring.

Could it be the heatsink is short circuit somewhere or could it also be the CPU bracket?

Some ideas on where I should look to fix this problem?

[piernov]

Re: Laptop only works without heatsink - HP ZBook 15 G1

Had a case where the balls under the PCH where cracked and screwing in (or unscrewing, can't remember) the heatsink made them not make contact anymore (since the board was flexing a little bit). Solved by reballing the PCH.
Also heatsink was slightly bent and shorted to the capacitors on the top of the GPU. Solved by bending it back and adding kapton tape around the GPU die (on top of the capacitors on the GPU) for good measure.

[ktmmotocross]

Re: Laptop only works without heatsink - HP ZBook 15 G1

reballing is nessessary? reflow will do it too

[piernov]

Re: Laptop only works without heatsink - HP ZBook 15 G1

Reflow killed it completely, so yeah reballing was necessary.