HP G61 with momentary power

[DCJack]

I have a G61 that powers up the button board for about two seconds and dies.

I the FETs test OK and I replaced the ISL power controller which is a common issue with these boards, but to my surprise the problem persists.

Anybody have any ideas?

P.S. The BIOS standby voltages, give or take, check out.

[Tuomo]

Re: HP G61 with momentary power

I have a G61 that powers up the button board for about two seconds and dies.

I the FETs test OK and I replaced the ISL power controller which is a common issue with these boards, but to my surprise the problem persists.

Anybody have any ideas?

P.S. The BIOS standby voltages, give or take, check out.

Sound like short circuit.

Try measure resistance to coils. Remove CPU and try if power stay on.

[DCJack]

Re: HP G61 with momentary power

Thanks for the advice Tuomo, but I am a little confused about the coils. Am I correct in assuming you mean resistance to ground from the coils (the large grey chokes)? How will this help?

Forgive the ignorance, but I am just a computer user with a basic understanding of electronics and a cheap SMD rework station.

As for the CPU, everything that can be removed has been. No RAM, CPU or BIOS battery.

[Th3_uN1Qu3]

Re: HP G61 with momentary power

Measure resistance across the polymer caps next to the northbridge, GPU if it has one, and southbridge. One of those chips may be shorted. If that's the case, you'll need someone with a BGA rework station to fix it for you.

[DCJack]

Re: HP G61 with momentary power

I've tested the polymer caps and none show a short much less a lower impedance than expected.

[Tuomo]

Re: HP G61 with momentary power

Thanks for the advice Tuomo, but I am a little confused about the coils. Am I correct in assuming you mean resistance to ground from the coils (the large grey chokes)? How will this help?

Forgive the ignorance, but I am just a computer user with a basic understanding of electronics and a cheap SMD rework station.

As for the CPU, everything that can be removed has been. No RAM, CPU or BIOS battery.

Yes resistance to ground.

If they show low resistance you know at this circuit has short circuit.

GPU and CPU have very low resistance so remove CPU before measure resistance.

[DCJack]

Re: HP G61 with momentary power

Found the problem! It turns out it was a bad coupling cap that was not quite shorted. It was a lucky find as it burned me when I was measuring something on the board.

[luktech]

Re: HP G61 with momentary power

What did u do next. Remove or you shorted it.

[DCJack]

Re: HP G61 with momentary power

Replaced it and they all lived happily ever after.