compaq laptop

[superdoyle]

I am working on a compaq cq61-429 for a friend and the problem is after about 30 seconds to a minute the screen goes blank. I done a complete tear down and cleaned it and the problem still persists. I'm hoping someone can point me in the right direction.

[999999999]

Re: compaq laptop

When it blanks, shine a flashlight on it at an angle to see if the images still appear on screen, if they do then the backlight has gone out and you'd want a replacement inverter board or to troubleshoot discreet components in the lighting subsystem

Otherwise, does the system seem to respond and be running stable (code)? Does it boot the OS, or if OS is running does it shut down through software (keyboard commands)? Try to determine if it is only the display going out or the whole system crashed.

[superdoyle]

Re: compaq laptop

Thanks for the reply, the black lights are working. when i tap on the left hand of the keyboard the screen flickers with a picture :note: the gpu is under the spot that i tap on. i rechecked all the connections and they are tight.

[999999999]

Re: compaq laptop

I can think of a few possibilities. Either the circuit board has a hairline crack breaking a trace(s), something surface mount has had it's solder joints cracked from physical shock, the GPU has broken solder joints from thermal stress, or the monitor connector (or wiring) has a break in it.
You might be able to figure out which it is by running the parts out of the case and applying different stresses to different areas.

Try hooking an external monitor up and see if the video blanks still, if so it should rule out the cable/connectors being the problem. Otherwise if it's the GPU, some people have reported success baking the mainboard in the oven, but I feel like that is a short term fix that will fail again. Someone might be able to reflow it with a hot air station, but with it failing the first time, it could easily fail again if that's the cause and solution.

Generalizing, it seems more likely the GPU itself given the time interval before it blanks. Don't know if it's still the case but many laptops have had an inherent flaw in their cooling, that they used the same heatpipe and fan to cool both the northbridge/GPU and CPU, but the fan throttles up and down based only on CPU temperature so any time the GPU is under heavy load and the bottleneck, it receives less than "ideal" cooling. Plus the goofball designers often put a thick silicone pad on it with much higher thermal resistance than other conventional heatsink-chip interface methods. I'm thinking of a few failed HPs back when everyone claimed nVidia had a solder ball problem but the problem only surfaced if the chips got really hot.

You might check HP's forums to see if others are reporting the problem and what their resolution is.

[superdoyle]

Re: compaq laptop

Thanks for the reply. I just took a heatgun to the gpu chip and let it cool for 30 minutes. Also i used the copper penny trick that everyone talked about on compaqs and hp laptops and it seems the problem is gone. I left it one for 30 minutes and the screen didnt flash or all those other things when a gpu gets hot.