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Macbook Pro A2141 820-01700-05 Wont turn on.

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cpuentes23

New member
Hi guys,

I got a 820-01700-05 logic board that won’t turn on after wake up from sleep with no signs of burned components or water spills. It is stuck at 5v and PPBUS seems to be shorted to ground.

PPBUS_G3H - 0.1V


In resistance mode:

PPBUS_G3H to ground: 17.7 Ohms
PPBUS_G3H to CPU coils: 18.4 Ohms
CPU coils to ground: 1.5 Ohms
PP2V5_ NAND_SSD to ground: 7.0 K Ohms

In diode mode:

CPU coils to ground: 001
Other big coils around: 007, 003, 002, 012, 015.


Any ideas would be greatly appreciated.
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

"PPBUS_G3H to ground: 17.7 Ohms"
Did you test with charger, or battery connected???
Allow 10-15s after power is removed, before checking diode mode, or ohm scale!

I suspect angle sensors issue.
Check U4802 signals, with lid closed/open.
 
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cpuentes23

New member
Thank you 2informaticos! Happy to be here!


Well, on "PPBUS_G3H to ground", I'm getting 0 Ohms with charger and 16.5 Ohms with battery connected.
In diode mode 0.173 with charger and 0.008 with battery.

U4802 signals - Lid closed.

Pin 1 - 0.001v
Pin 2 - 0.0v
Pin 4 - 0.005v
Pin 6 - 0.0v

U4802 signals - Lid Open.

Pin 1 - 0.006v
Pin 2 - 0.0v
Pin 4 - 0.0v
Pin 6 - 0.0v

Just in case - in resistance mode

Pin 1 - 4.23 MOhms
Pin 2 - 9.6 kOhms
Pin 4 - 50 KOhms
Pin 6 - 7.5 Ohms

Thank you!
 
2informaticos

2informaticos

Administrator
Staff member
As expected, your ptoblem is caused by lid signals.
Missing 1V8_SLPS2R to U4802 must be corrected.
Check the trace to other points of the same power rail.
If broken, you can run a wire.

NOT expected, to see you still checking diode mode with power on the board; STOP that!
 
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cpuentes23

New member
I thought maybe a component was causing a short to ground on 1V8_SLPS2R rail? sorry, I'm still learning.

I've been checking other points of the same trail and the line seems to be broken, any ideas where I can run a wire?

Gracias!
 
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cpuentes23

New member
No, Im not getting 1.8V on that line. I was also checking voltages that U7800 outputs and nothing. May U7800 be bad? Let me know what you think.

Thanks.
 
2informaticos

2informaticos

Administrator
Staff member
So no voltage at L7813?
Check diode mode to ground there.
Be sure R7813 has 0 ohm.
If all good, should change U7800.
 
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cpuentes23

New member
L7813
With charger: 0.0v
Diode mode to ground: .003V
-----------------
R7813
0 Ohm.

You think reflowing the chip could be an option before replacing it?

Thank you.
 
2informaticos

2informaticos

Administrator
Staff member
Don't write end "V" after diode mode reading.
We don't want to make confusion with voltage measurment.
I hope you've got 0.003 witout charger connected.
For low values (under 0.005), switch to ohm mode.

You can try first injecting voltage.
There are many components connected, not only U7800.
Is not pure short, but an IR cam may help you to find the culprit.
Remove CPU/GPU heatsink first.
Then start injecting 1V; you can slowly increase until 2V (no more).
Set the amp limit to max first, on the lab PSU.
 
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cpuentes23

New member
Got it!

Yes, I've got 0.003 without charger connected / in resitance mode: 6.1 ohms

So just to confirm, should I inject voltage to the 1V8_SLPS2R rail?

Thank you!
 
2informaticos

2informaticos

Administrator
Staff member
Of course, on the power rail where you have the short.
You probably can't heat anything too much, with 6 ohm resistance; unless something enters in thermal avalanche.
IR cam will help you to detect small temperature differences.
 
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cpuentes23

New member
Well, the only component that is getting hot is the Apple T2 chip when voltage is injected. Could this be the issue?

Thank you.
 
2informaticos

2informaticos

Administrator
Staff member
You need to get the touch ID from the same board found the replacement T2.
If not, need to bring the machine to an official Apple service; they can pair T2 and touch ID again.
 
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