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Old 06-26-2018, 09:36 AM   #1
Andreasbest
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Exclamation Dell Inspiron LA-D801P Motherboard completely dead

Hello.
Today i received a Dell Inspiron with LA-D801P motherboard.
Customer's son spill some orange juice on it from the bottom ventilation holes and laptop completely died.
I clean up everything with Isopropelene Alcohol but still completely dead, no power, no leds.
I receive voltage at the adaptor input in board and that's all.
Any help appreciated, schematic attached.
Thank you in advance!!!
Attached Files
File Type: pdf LA-D801P REV 1.0 (A00).pdf (3.27 MB, 182 views)
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Old 06-26-2018, 10:00 AM   #2
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Check the ALW (always on) power rails , and check for corrosion under a microscope
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Old 06-26-2018, 11:09 AM   #3
Andreasbest
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

No corrosion at all, checked it.
What is the ALW power trails?
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Old 06-26-2018, 11:38 AM   #4
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Test the voltage on pin 2 of PL1, pin 1 of PL2 , Pin 1 and 4 of PR703 , Pin 9 and 19 of PU102
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Old 06-26-2018, 01:02 PM   #5
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Also check voltage at pin 5 of PQ740 N-type Mosfet, should be Vin-19.5v for dell. Same Mosfet, pin 1, should be same voltage if conducting. Same Mosfet, pin 4, should be high, around 32v.
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Old 06-27-2018, 02:22 AM   #6
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

PL1 has 19v in both pins, PL2 no voltage at all.
PU102 is 0v at pin9 and 5v at pin 19
PR703 is not present (check picture top right)
PQ740 is 19v in pin1, pin4 24.7v, pin5 19v.
Attached Images
File Type: jpg PR703.jpg (560.5 KB, 128 views)

Last edited by Andreasbest; 06-27-2018 at 02:28 AM..
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Old 06-27-2018, 05:03 AM   #7
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Ok, next test voltage on PU100 pins 2,11,12,17,19
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Old 06-27-2018, 08:12 AM   #8
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

PU100 :
pin2 19.6v
pin11 4.5v
pin12 2.3v
pin17 3.3v
pin19 0v
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Old 06-27-2018, 08:45 AM   #9
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Ok, so you`re missing +3VALWP , next,with no power to the board test PR121 if its on the board, it should be 0ohms and/or check for short to gnd pin 19 of PU100
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Old 06-27-2018, 02:39 PM   #10
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Didn't manage to find PR121 but pin19 has a shortcircuit (0.004Ω) with ground
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Old 06-27-2018, 04:19 PM   #11
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Ok , so it might be PU100 that needs replacing, or some other part on the +3VALWP rail. Take off 1 at a time PC106 ,PC107 ,PC108 , and PC109 .check for short after removing each ,and put back on if the short is still there. If its still short after checking those remove PU100 and check short on pin 19 again, if its gone replace PU100 .
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Old 06-28-2018, 02:22 AM   #12
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Since i don't have boardview i'm not sure what smd are pc106,pc107,pc108,pc109.
Do you think they are these 4 smd bottom right of the PL100?
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File Type: jpg 20180628_112310[1].jpg (581.7 KB, 116 views)

Last edited by Andreasbest; 06-28-2018 at 02:25 AM..
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Old 06-28-2018, 03:17 AM   #13
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

In this case, yes it will be those 4 big caps to the right of PL100.I can see some crap in between the caps.Put some liquid flux around those caps and heat that area up and clean it up with a brush. Test if the short has gone, if not you have a choice, take off PU100 first or the 4 caps,the caps are all the same value so can`t mix them up.
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Old 06-28-2018, 03:36 AM   #14
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

remove pjp102 solder with desolder wick and see if 3.3 volt comes to pl100
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Old 06-28-2018, 03:56 AM   #15
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Removed all capacitors and PU100 but shortcircuit is still there.
Removed PJP102 (with ic and 4 caps off) and shortcircuit gone.

Last edited by Andreasbest; 06-28-2018 at 04:00 AM..
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Old 06-28-2018, 04:38 AM   #16
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

put ic and caps back in plase and see if on pl100 u have 3.3 volts (all with pjp102 still desoldered)
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Old 06-28-2018, 05:19 AM   #17
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Ah i missed out pjp102,so the short is on +3VALW ,its going to be a difficult repair, unless you can find any obvious damage to any of the parts on that rail.
Check IC`s for any burns or damage on the pins UA1,UZ3,PU703,UE1 and check the CMOS battery area .
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Old 06-28-2018, 05:48 AM   #18
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

Put back everything in place.
As i said without jumper the shortcircuit is gone but still no voltage at PIN19.

Last edited by Andreasbest; 06-28-2018 at 05:52 AM..
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Old 06-28-2018, 06:15 AM   #19
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

page 4 of schematic, followind 3.3 volt line , check following pjp point to track where the short is.

try remove pjp501... still short on pjp102 +3VALW side ?

remove pjp801, then jp5, then jp9.

wich one remove the short ?
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Old 06-28-2018, 06:17 AM   #20
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Default Re: Dell Inspiron LA-D801P Motherboard completely dead

@Dellxps15 ,do you think pin 12 of PU100 is low 2.3v
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