Hi,

have an issue with an Acer 5741G (Compal LA-5891P) that turns off randomly.

Seems that is a temperature problem, but the thermal paste and the heat pipe assembly has been changed.

The first boot it is stable 2 minutes or so, then it turns off, since this time it only stays on for 6 or 7 seconds. (sometimes a bit more)

All voltages are good and also ddr and cpu have been tested.

The weird thing is that it can be in bios setup for more than 2 hours without any problem. (only if bios setup is enter while it is cold enough)

Power button circuit is tested and has no problems in it, also ec-bios and pch-bios are good.

Can someone give me a hint to solve the issue?

Is the CPU voltage stable? use an oscilloscope

Yes cpu voltage is stable and has no ripple. (only has the small variations that are normal during boot)

I have activated F12 in bios setup in order to select boot device, and when boot, if detects F12, shows the boot menu forever, but if select a device and press enter, it turns off.

Regards.

remove battery cmos

The cmos battery had been removed at first, and did some test without it, but now it's soldered again.

I will remove again and continue the test without it.

I have put a password on boot, and it start always asking for the password, and doesn't turns off, only when I write the password and press enter, it turns off.

A very weird thing.

Hope someone has had this problem before and can help me.

Thanks.

If U9 is installed, raise the 6th pin. If this solves the problem, replace the graphics processor.

PU30 is not soldered in the circuit since I started to make the tests, but I have not tested U9.

I will try it and post if success or not.

Regards.

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Posted after 2 hours 38 minutes 41 second:
hi, majemus I have removed U9 and it works and loads windows.

I will put a new U9 and will test. (it's easy than change the gpu)

I will let you know the results.

If you replace the U9, this will not solve the problem. The problem is with the thermal diode of the GPU. When replacing the U9, you will have a thermal effect on the GPU and it will work, but it will not fix it.

It works ok without U9, but I have ordered a new gpu.

I think the new gpu will solve the problem definitely.

Thanks for your help.