HP Pavilion 15-N096SA (U83) missing +12vALW

[CuriousJohn]

HP Pavilion 15-N096SA (U83)

Hi folks can you help me please find where +12vALW is generated as its missing and service manual is not helpful to locate it.


With ref to U83 schematic taken from this post: https://www.badcaps.net/forum/showthread.php?t=47691

Symptoms are no start up, no lights anywhere but power button flashes when pressed but not fast fairly slow once every few seconds and there are no lights at all from the power socket so thats where i started and discovered the missing +12vALW. it seems to be absent all over the board.

all present and correct:

+3vpcu,
+5vpcu,
+3vs5,
+5vs5
+Vin
+Vad


The block diagram indicates +12vALW comes out the discharger IC but the schematic has no reference to it anywhere that i can find and have studied it for a while waggling my finger at the EC. This is my first go at laptop repair so if you could be patient and point me in the right direction it would be appreciated.

[Techtiger]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

most likely from PU6 discharge IC

[CuriousJohn]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

Thanks for the response i assure you i looked at PU6 for a long time, with ref to attached schematic of it with my findings can you see it? I need to look again at Pin 17 Vout not sure about that one. Also Vin according to data sheet should be 8v min so thats an issue to perhaps.

Data sheet: https://cdn.badcaps-static.com/pdfs/...0c828c330e.pdf

PU6 doesnt appear to be running its why i wiggle my finger at EC but not certain until I find this pesky +12vALW. I have seen mention of Q33 from other models but no labelling as such here.

[mcplslg123]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

Pin20 VIN should be 19V. Check PR118 as it seems faulty. You are getting 19V at one end but only 1.36V at the other end(vin side)-should be 19V at both side. Unless VIN is 19V ,ic is not supposed to work either.

[CuriousJohn]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

Cheers mcplslg123 i have just rechecked voltages ether side of pr118 and in fact Vin side is 0v so remembering its more likely for a cap to go SC than a Resistor going OC i just done what i should have done first time and measured continuity at junction of these. Long story short looks like PC145 is short to ground which means i get to fire up the new rework station, today is the day.

[CuriousJohn]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

Ok scrub that last post lol

Cap is fine resistor is high out of circuit reading 1K it should be 22 ohm so todays lessons are remove the biggest suspect smd component first and dont forget to remember 15 ohm is not S/C even if the meter beeps like its short.

Cup of coffee and fit new resistor plus put cap back then, its the size of a damn flea!

[ktmmotocross]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

u have big mistakes in your picture. u have +VAD on one pin and no on other pin

better measure again everything

[CuriousJohn]

Re: HP Pavilion 15-N096SA (U83) missing +12vALW

Ok i missed some things on my sheet like pin 6 and 7 for instance 3VSUS is peaking with the flashing power light between 0v to 1.6v could be higher my meter is basic i know all supplies coming in to chip are good.

problem appears to narrowed down to internal short of PU6 between Vin and ground as just replaced PR118 due to it being way out of tolerance some 1K when its a 22 ohm part (220) and still no VAD on PU6 side of it, PC145 defo not short removed for now and inspected tracks and pads for shorts using microscope.

Contemplating the need to replace PU6 "P36J5934", is this a common part to fail?