Macbook A1502 - 820-3476 Trackpad Not Working

[Instafixx]

Hello,
I have a Macbook 820-3476 with no trackpad. I replaced the cable and the trackpad as well from a donor laptop but its still the same. Can this be a board issue ? The board is clean though.

 

[2informaticos]

Check L4807 and R4808.
Bypass them for test...

 

[Instafixx]

What do you mean by bypass them ? Should we remove them ?

 

[2informaticos]

Solder a tiny wire...

 

[Instafixx]

Ran a jumper wire from Point 2 of L4807 to Point 2 of R4808.

The device didnt turn on. Only Backlight was there.
Removed the jumper . The device turned on.

 

[2informaticos]

What???
I said to bypass 2 components; not to tied them together.
Didn't think that shouldn't join 3V3 and 5V power rails???

 

[Instafixx]

Sorry but i have not understood what you mean bypass. Should we remove the component and run a wire from point 1 to point 2 ?

 

[2informaticos]

No need to remove them, once you run the wire over.

 

[Instafixx]

Did that. Didnt Work

 

[2informaticos]

So, you have correct voltage at pins 1 & 4 of J4800?

Check traces between J4800 and U4801.
Also resolder them.
Keyboard works correctly?
Do you have 0V at BUTTON_DISABLE?
Be sure R4800 is good.

If still not working, replace U4801.

 

[Instafixx]

Correct Voltages at Pin 1 and Pin 2.

Keyboard Works correctly.

Yes 0V at Button Disable.

R4800 Voltage Cycling between 1.4 to 3.2V continuously.\

Note - All above voltages are taken with the bypass done on L4807 and R4808.

What do you mean by check traces ? i didnt understand that

 

[2informaticos]

Check traces continuity between trackpad connector (J4800) and U4801.

I recommend to try more trackpad cables.
2 from 3 (new chinese) cables failed for me time ago.

 

[Instafixx]

Customer didnt give me time was in a hurry. Hence returned.

 

[Instafixx]

Hi,
Same model with Same iSsue .

I removed L4807 and R4808 to test. Still does not work.
I checked voltages at J4800 Pin 1 and Pin 4 are Zero. (Checked With the above 2 removed).

I put them back and Check Voltages.
Pin 1 is 3.3V
Pin 4 is 0V.

Please suggest

 

[2informaticos]

"I removed L4807 and R4808 to test. Still does not work.
I checked voltages at J4800 Pin 1 and Pin 4 are Zero. (Checked With the above 2 removed)."
What do you expect, cutting off the power rails???

Possibly L4807 is bad; bypass it.

 

[Instafixx]

By Bypass you mean tieing both ends of L4807?

 

[2informaticos]

Exactly...

 

[Instafixx]

After bypass i get Voltage at Pin 4. But still no trackapd.

 

[2informaticos]

So KB is good, only TP not working?
Tried known good TP board/flex?

 

[Instafixx]

KB was always good.
Let me try with Flex