Question Laptop not starting, power LED stays on for 3 seconds then off ?

[Epyc Mihai]

I have recently opened my laptop to clean the fan, it was working before, but after i correctly assembled it, it did not want to start. The power led would stay on for 3 seconds and then turn off again each time i would try to power it. No fan or any noise whatsoever. I am sure it is not an AC Adapter or Battery problem, because both are new. It seems there is a problem with the motherboard, but i don't know what. Thanks for the help in advance.

Toshiba Satellite L750

Specs:
DDDR3 8GB RAM
CPU Intel Core I3-2310m
GPU Nvidia Geforce GT 525M

 

[Darkbreeze]

I would take it apart again and make CERTAIN that you plugged back in each and every little connector and double check all the rest. Any little thing not right can result in complete failure to work properly and it's very easy to overlook something like the ribbon cable going to the display or fan connector not fully seated. Anything. Generally it's going to shut off if there is no fan RPM signal after 3 seconds. Make certain that all fan connectors are plugged in AND correctly oriented because I HAVE seen people accidentally install the tiny fan connectors in reverse on some models.

Obviously, it's something you either did or overlooked, so go back and do it again a little more carefully. Often if you can find a complete teardown and reassembly on Youtube it will help immensely with not overlooking any steps.

 

[penguintech]

Did you wear a static strap when you disassembled and reassembled the laptop?

 

[Darkbreeze]

That is unlikely to be relevant. I've build literally hundreds of computers and disassembled many, MANY laptops, and I've never worn one. It's an extremely uncommon occurrence for ESD to truly damage a component in the real world while you're working on it. Possible, sure. Likely? Not at all. Besides which, that couldn't possibly have anything to do with the fan not operating.