shorted power rail - drawing 3.5 amps but no heat?

[survivalbloke]

This board is out of an HP laptop. There is no voltage present at pin 8 of the Winbond BIOS chip. A nearby coil is a near dead short to ground. Injected 1v and it drew 2.8a but nothing was warm on the board. Then I upped the voltage to 2.5 and 3.5a were drawn, but still no heat. Is that crazy?

[mon2]

Re: shorted power rail - drawing 3.5 amps but no heat?

Could the heated part be the CPU that may be with a heatsink?

[survivalbloke]

Re: shorted power rail - drawing 3.5 amps but no heat?

Could the heated part be the CPU that may be with a heatsink?

AW MAN! I bet that's it.

[gs84]

Re: shorted power rail - drawing 3.5 amps but no heat?

Great! Maybe better to begin from MB model and the pictures? How you measure the temperature: by finger, lips?

[survivalbloke]

Re: shorted power rail - drawing 3.5 amps but no heat?

Great! Maybe better to begin from MB model and the pictures? How you measure the temperature: by finger, lips?

Sure thing! I was using a thermal camera which is normally how I find shorts when I inject voltage. This board is LA-D704P Rev 4.0 Do you want pictures of the board?

[gs84]

Re: shorted power rail - drawing 3.5 amps but no heat?

mb from hp, near some coil... What kind of help do you expect with such inputs? Which coil? if no position at the MB silk, then show it on the picture

[survivalbloke]

Re: shorted power rail - drawing 3.5 amps but no heat?

mb from hp, near some coil... What kind of help do you expect with such inputs? Which coil? if no position at the MB silk, then show it on the picture

I'm with you, I'm with you. I'll look for a boardview and schematic, then post pics.

[gs84]

Re: shorted power rail - drawing 3.5 amps but no heat?

ok, I'll wait.

[mcplslg123]

Re: shorted power rail - drawing 3.5 amps but no heat?

If you can just mention the coil number, i can tell you which rail it is as i've worked on plenty of this model. Schemaic is not available for LA-D704. Whatever schematic you see labelled as D704 is not an exact schematic. Its a blunder to inject 2.5V on any coil.

[usyusy]

Re: shorted power rail - drawing 3.5 amps but no heat?

Also possibility exists that SIO is short

[survivalbloke]

Re: shorted power rail - drawing 3.5 amps but no heat?

If you can just mention the coil number, i can tell you which rail it is as i've worked on plenty of this model. Schemaic is not available for LA-D704. Whatever schematic you see labelled as D704 is not an exact schematic. Its a blunder to inject 2.5V on any coil.

What voltage and amperage to you use most of the time for injection?

[mcplslg123]

Re: shorted power rail - drawing 3.5 amps but no heat?

1V/5A and sometimes even 1V/10A.