HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

[flasheverything]

HP IBT00 LA-3262P (osp) Rev: 1B - problem with reversed polarity of charger (not my doing) and wouldn't turn on

I've checked this forum and there was another case where someone's la-3261p with reversed polarity and didn't turn on. My problem is that only one of the mosfets close to the dc jack has 19v going into source, but not to drain. The mosfet right after has nothing into source or drain. There is a clear schematic for this but I have checked all caps, transistors, ic, transistors and they appear to be fine. I checked the mosfet and it appears to be fine and also swapped for another p-channel mosfet. Maybe I'm missing some signals.

There is a LM393 Dual Differential Comparator which has a hole in it and would be busted, but I don't think it has anything to do with the power delivery

http://imgur.com/a/v0KKv

here's the schematic:
https://cdn.badcaps-static.com/pdfs/...ac17446eca.pdf

I'm not getting PL2, PL4, OR B+

[flasheverything]

Re: HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

PL1 is 19 volts and going into VIN, then goes into pq5 and source side of pq4, but nothing after

[diif]

Re: HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

Which LM393, your red box obscures the markings.

[BlueMidnight]

Re: HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

For the input MOSFET PQ3 to turn on, ADP_EN# must be low. And the state of ADP_EN# has everything to do with PU25 (which appears to be the IC with the nice big hole in it). You'll see on page 50 that if PU25 is gone, then ADP_EN# will just rise up to the voltage of VIN.

There might be more things wrong too, but that's a start.

[flasheverything]

Re: HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

For the input MOSFET PQ3 to turn on, ADP_EN# must be low. And the state of ADP_EN# has everything to do with PU25 (which appears to be the IC with the nice big hole in it). You'll see on page 50 that if PU25 is gone, then ADP_EN# will just rise up to the voltage of VIN.

There might be more things wrong too, but that's a start.

I'll get a replacement LM393 and see what happens. I can see on page 41 of the schematic it has to do with the PWR_OK circuit and has pu25 LM393 which has the hole in it.

[flasheverything]

Re: HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

Which LM393, your red box obscures the markings.

the red box is pu25 which is LM393M_SO8 and has a hole in it

[BlueMidnight]

Re: HP 6910p IBT00 LA-3262P Rev: 1B reversed polarity

...I can see on page 41 of the schematic it has to do with the PWR_OK circuit and has pu25 LM393 which has the hole in it.

Page 41 has another LM393, but it is completely separate. That circuit is responsible for signaling that all the main voltages have stabilized later in the power-up process.

The circuit on page 50 is responsible for recognizing that the (proper) AC adapter is plugged in, and signalling that the input MOSFETs should be turned on.