Dell studio 1737 turning off

[wirelessguy]

I have a customer that brought in a studio 1737 that was not charging. I tested the ac adaptor and putting out correct voltage. My next step was to replace the dc jack/usb board..didnt fix problem. I then replaced the motherboard and everything worked fine for about 2 months. Laptop brought back in not doing anything after she said the laptop was running on battery and battery was depleted. Took laptop apart and finally got it to post, but laptop shuts down after anywhere from 5 seconds to 3 minutes. Went in to Diagnostic mode and laptop shutdown when it got to memory tests. CLeaned memory and tried 1 at a time in differents lots. Tried new piece of memory..same. took out everything but motherboard..same. Reaplied thermal compound on processor...same. Any suggestions? Bueller...Bueller....Bueller.

[osprey4]

No Dell portable post codes or beeps on startup? If you boot straight into the BIOS, does it still shut down?

[wirelessguy]

i can go into bios and let it set..sometimes 10 seconds..sometimes 3 minutes then it will shutdown. It doesnt seem like a heat related problem. I can hit f12 at startup and go to the diagnostic test..same thing there shuts down at different times.

[wirelessguy]

sometimes the machine will turn on..no screen but there are some flashing lights.
the audio mute light will flash and the volume up/down lights are solid..no other lights on panel.