Hello everyone..

this laptop came with no start symptoms, when pressing power button lights come on for 5 seconds then off till pressing again, and also 5 seconds then off, no start and no display at all..

I've opened the laptop, disconnected CMOS battery and main battery, pressed the power button for 10 seconds, reconnect CMOS & main battery again, press the power button and the laptop started working flawlessly passing all tests.. given to the customer

a month later it came back with exact same symptoms, resetting CMOS also helped but this time I've flashed the main bios and replaced CMOS battery with new one..

two months later it came back again

where to dig ?

Мне помогла прошивка биоса и мультиконтроллера

Try to replace bios chip with new one. Battery alive? When it often extremely shutdown - it may be reason of damage bios. If you replaced CMOS battery - check voltage after few hours, it should be same.