820-3787-A No Trackpad no Keyboard

[Sr. Robot]

Hello, hope you guys are great.

I am very new to this so bear with me please.

I have a 820-3787-A with no trackpad and no keyboard. I measured power on J4813 (keyboard connector):

1. PP3V42_G3H_TPAD is 3.4
2. PP3V3_S4_TPAD is 2.8v all across the rail.

U4801 doesnt seem to be corroded or damaged. Im trying to figure out where is PP3V3_S4 created. I belive in U1900 ?

U1900 doesnt seem damaged also. But its measuring 1.1v on pin 14.

 

[2informaticos]

First of all, welcome to the forum!

As page 81 shows, 3V3_S4_TPAD comes from 3V3_S4_FET (Q8000).
Post Q8000/2 voltages.
Check diode mode on 3V3_S4_TPAD w/ and w/ trackpad connected.

 

[Sr. Robot]

Thank you for your welcome.

From Q8000 i get 2.8v from pp3v3 s4 and 3.3 from pp3v3 s5

Diode mode 3V3_S4_TPAD on pin 20 of J4813

w/o trackpad connected: 0.139v

w/trackpad connected: 0.139v

whats the purpose of the diode mode measurement in this case?

Thank you.

 

[2informaticos]

Looks like no short, so probably bad Q8000, or incorrectly controlled.

I asked you to post voltages for two transistors, not two pins of one transistor...

 

[Sr. Robot]

Yes, sorry. Can it be any of the Q8000's?

1. Q8000 =

Source 3.3v - Gate 3.25v - Drain 2.8v

1. Q8050 =

Source 5.0v - Gate 0.0v - Drain 5.0v

 

[2informaticos]

I asked about Q8000 AND Q8002!!!

 

[Sr. Robot]

Q8002:

Gate: 3.3v - Source: 0v - Drain 0v

 

[2informaticos]

Q8002 is dual MOSFET, did you check at pins 1, 2, 6???

Change Q8000, just in case.

 

[Sr. Robot]

Replaced Q8000 and now we have keyboard and trackpad. Thanks a lot for your patience and guidance.