HP 15-ab271sa repair

[case sensitive]

Hi, I have an HP 15-ab271sa that I'm trying to repair, the board (Quanta X12A) doesn't power on.

The problem manifests itself in one of two ways:
1) The LED on the DC jack switches off briefly when the power button is pressed (then back on) and the 3.3V rail powers on for a few seconds before switching off.
OR
2) (rarely) the DC jack LED stays off after pressing the power button and 3.3, 5 and VCC_Core all power on (and stay on). 1.05V and 1.35V (RAM) are not present. When this happens HWPG (power good?) is 0V which I assume is why I don't get 1.05 and 1.35V.

When I got it to repair the laptop did very rarely successfully power on into Windows but doesn't anymore.

Boardview and schematics have been posted by other users here: https://www.badcaps.net/forum/showthread.php?t=53625

Any suggestions on where to look next? Thanks in advance.

[mcplslg123]

Re: HP 15-ab271sa repair

All indicators are towards AD_ID problem. Probe AD_ID voltage at dc jack as well at SIO pin. This is a common fault with this model. If you have a spi programmer, take backup of your existing bios chips and flash known good bios with clean me.

[case sensitive]

Re: HP 15-ab271sa repair

0.6v for AD_ID at the DC jack and SIO, AD_TYPE is 0.6v too.
I have a spi programmer so will try that, thanks.

[case sensitive]

Re: HP 15-ab271sa repair

OK after reprogramming the bios chip there is some progress. The board will now reliably attempt to power on and the power LED on the other side of the board (from DC jack) now turns on (didn't happen before). It will then power off and the DC jack and power LED will flash once before turning off again.

As far as I can tell 3.3, 5 and 1.05v are powering on but it's so quick it's had to catch with the multimeter.

Is 0.6v AD_ID correct? The behaviour is the same when the battery is connected.

[mcplslg123]

Re: HP 15-ab271sa repair

0.6v at AD_ID is correct.

[case sensitive]

Re: HP 15-ab271sa repair

All the main power rails except VCC_CORE seem to be powering on now (which is strange because I had 1.7v on VCC_CORE before flashing the bios).

So currently what happens when I press the power button is:
1) 3.3 and 5v turn on
2) board powers off (leds and 3.3/5v turn off)
3) board powers back on
4) 3.3, 5, 1.05, 1.5 and 1.35 (ram) power on for less than a second, no VCC_CORE
5) power off again

VRON from the SIO is 0v but I'm not sure at what point that is supposed to turn on.
VR_ENABLE and VR_READY are both 0v too.

Thanks for your help so far, is there anything else that is a common problem on these boards that is worth checking?

[mcplslg123]

Re: HP 15-ab271sa repair

Did you take backup of your original bios?? If yes, flash it back and check again whether you have VCC_CORE. If that's the case, then perhaps new bios flashed may have issues. BTW, 1.8V is present??

[case sensitive]

Re: HP 15-ab271sa repair

I have a backup so can try flashing that back.

One thing I didn't notice before is that as soon as I plug the charger in (before pressing power button) the board actually powers up the 3.3, 5 and VCC_CORE rails (I just thought it turned the LED on), no 1.05v though.

Kind of stumped at this point, all the power rails are there at various times just never all at once and it clearly shouldn't be powering on the moment the charger is plugged in.

I can't see any mention of a 1.8V rail in the schematic. VCC_CORE is 1.7V though, is that what you mean?