[SOLVED]3476-A No TrackPad but keyboard and click works

[dam1inc]

have a wd 820-3476-A trackpad not working. connected USB keybpard and mouse and works...just trackpad doesnt work...all keys work and click button on trackpad works.

all voltages seem to be present but i reballed U4801 just in case also bought new trackpad/flex but still the same.


here is Diode Mode readings of J4800

1 443
2 695
3 695
4 683
5 01
6 689
7 689
8 689
9 689
10 690
11 690
12 0
13 689
14 689
15 689
16 689
17 689
18 689



any tips would be greatly appreciated

thanks

 

[dam1inc]

also when i connect flex and measure pin1 = pp3v3_tpad_conn, it fluctuates between 1.3 and 1.8v

edit. nevermind pin1 is solid 1.8v but still nothing

 

[dam1inc]

ok so when trackpad is not connected i get 3.3v on pin 1 but when connected i get 1.8v. i read somewhere here that it could be bad r4808 so i removed and ran jumper since its 0 ohm, also read another where it could be U8000 switch, how can i test if its the switch?

 

[dukefawks]

So with R4808 bridged is 3V now present with trackpad connected? You also have to wonder why it failed and it could be a bad trackpad too.

 

[dam1inc]

yeah i thought bad trackpad too but i have two of the same macbooks both waterdamaged and tried with both of those trackpads and thought maybe those were bad so i bought two new ones and still same thing
3.3v is only present on pin 1 if trackpad is disconnected, when trackpad is connected it is 1.8v


what are some possible reasons for voltage dropping on this pin?

 

[dukefawks]

A bad R4808 or bad trace/connector. Check on any other component that has 3V3_S4 going to it if that also drops to 1.8V, if 3v3_S4 drops to 1.8V elsewhere on the board then it points to a dead U8000.

 

[dam1inc]

R4808 was removed.
I checked the her components and 3.3v is present. Only on the pads of r4808 and pin 1 on j4800 is it showing 1.8v while trackpad is connected.
You mentioned bad trace. Does that mean that the circuit leading to the pads on r4808 are bad?
And if that's the case how does one fix this? Am I supposed to run a jumper from closest 3v3_s4?
Thank you for the help

 

[dam1inc]

Ok so I ran a jumper from c3510 to pin1 and it solved my problem. But do I leave it like this or is there a real fix for this?

 

[dukefawks]

As long as 3v3 is getting to the trackpad and the jumper wire is secure it will be fine.

 

[dam1inc]

Ok cool, then we can mark this one as solved. I really appreciate your help too. so thank you