Diagnose a dead motherboard

[nl4m]

I have a laptop that does not turn on. When I plug in the power cable only the battery light comes on. I push the power button but the computer never turns on... I want to find out what the problem is. How do I test to see if the Motherboard is defective, or if it's the CPU that is defective? The ram I've tested by putting it in another computer. I just need to know how to test the motherboard and the CPU to see which one is defective, how do I do that? PLEASE HELP!!!!!

[Yellow Pasque]

Theoretically, you would try the CPU in another system with the same socket and/or use a different CPU for the mobo in question. Of course, that's not always feasible, so you may have to take it to a repair shop.

Keep in mind that it could be the battery or power supply circuitry (which I guess is part of the mobo).

[tgalati4]

Pull the battery. Try to boot on wall power alone.

[nl4m]

I tried to boot without the battery it does not help. I let the battery charge and booted from the battery alone, it does not help. The computer wont turn on. I tried booting without the ram, does not help. The power cable is not an original, but there is still power going through the computer.

So the only way to test the CPU is to replace it, or try it on another system? If the CPU fails then that's the problem. If it passes than is must be the motherboard? Can it be a bad HDD drive that's preventing the machine from powering up?

What's the "power supply circuitry"? Does that mean I'd have to replace the motherboard, or only a part of it?

[tgalati4]

It could be the power brick. Try another one.

[Grenage]

Can it be a bad HDD drive that's preventing the machine from powering up?

No, a HD isn't required to boot a machine; you'd leave that unplugged while testing.

Probability of failure is usually PSU > Motherboard > CPU. I've never actually seen a stock-clocked CPU fail, but it does happen.

[nl4m]

It's a laptop. Isn't the power supply build into the computer? If the power supply went bed the motherboard would need to be replaced, on a laptop, right?

If it's the CPU that's the problem, wont at least the power light turn on? The whole laptop is dead, excluding the battery light.

[Grenage]

It's a laptop. Isn't the power supply build into the computer? If the power supply went bed the motherboard would need to be replaced, on a laptop, right?

They are usually external on laptops.

If it's the CPU that's the problem, wont at least the power light turn on? The whole laptop is dead, excluding the battery light.

I would personally expect more than just a battery light if it was the CPU, so I'd lean towards motherboard or PSU. Unless you have some kit to test the PSU output, or a spare motherboard/cpu, you're a bit stuck.

[nl4m]

By PSU you mean the AC/Power cable? There's a normal 19v flowing through it.
I've read on the net that some motherboards beep when the CPU is bad, other motherboards don't... This varies by model?

[cascade9]

Yep, that varies by model and the error as well.

They are usually external on laptops.

Yeah, true. But there is still a power conversion going on (12v to 5v/3.3v or, similar).I agree, power supply, (or conversion) is probably not the problem though.

@ nl4m- try holding down the power button for a while, a long while. Up to 60 secodns. Sometimes that forces the CMOS to clear, and has given new life to laptops in the same situation as yours.

The CMOS should clear with 10-20 seconds, but holding it down longer wont hurt.