Hello
Measure the voltage on the coils and see that the voltages are generated and their size is normal. They should not drop and should be stable.
If all the voltages are generated, you have no problem in powering the device and you should look for the problem in the signal section.
The first task is to change the RAM and processor, etc.
Also, test the image output with VGA output.
Sometimes the BIOS program can solve your problem.
Checking the crystal with an oscilloscope and replacing it if there is no suitable clock.
From here on, the chipsets will be affected and the graphics chip, if it can be removed, will be removed from the circuit.
The PCH chip should be reballed..
According to your troubleshooting, any of the above may restart your device.
