This HP DV9000 boots up fine but there is no display video. I did some
checking and found out this is a very common problem.
http://www.pointoflaw.com/archives/2...vidia-clas.php The GPU
overheats and then the video stops functioning. I disassembled it and found
the heat sink vents clogged with dust. I used my new, economical, 852D
rework station to try and reflow the solder on the GPU though I don't think
it got hot enough to melt the solder. I should have tested the external
video before disassembling the entire thing but now with just the power
adapter and RAM plugged in, the external video is working but the laptop
screen flashes dimly once and that's it. My question is, since the external
video is working, (it displays "No OS found,") does that mean the GPU is
working fine and there is a problem with the laptop screen? Before
disassembling it I tried using the special function key to switch the
display output to the external monitor without the external monitor plugged
in to see if it had inadvertently been switched to the external monitor only
setting. That didn't work but now I'm wondering if with all the key pressing
when there was no video, perhaps I left it in the state where it's now
switched to external video only. In the interim, the CMOS battery was
removed and I was wondering if that would reset the video to enable the
laptop display.

Let me summarize.

1. Unit came on. You could hear the Windows logon wav file. No display on
screen.
2. Disassembled unit. Cleaned fan and heat sinks. Used rework station in
attempt to reflow solder to GPU.
3. Reconnected the RAM and power supply with the motherboard attached to the
case with a couple of screws.
4. Powered on, no laptop video but video works to external monitor.
5. Is the GPU good?
6. How to proceed next?

Thanks for your reply.
--
David Farber
Los Osos, CA