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A2338 M2 820-02773 5v 0.10ma

overshoot

overshoot

Member
Hello,

I've got this board that stopped working after, that's what the customer has reported, the trackpad stopped clicking.
Board looks pristine, no liquid damage that I can spot.
I was getting 20V 0.01A with battery plugged in.
Without battery, I am now getting 5V with 0.1A current drawn.

Here are some readings:
PPBUS_AON = 12,3v
PP3V8_AON = 3.8v
PP5V_AON = 5v
PP1V8_AON_MPMU = 1.8V
PP1V8_AON_SPMU = 1.2V
PP1V2_AON_MPMU = 1.2V
PP1V2_AON_SPMU = 1.2V

One thing that worries me is that the only part that warms up is U1950 which is the SEP EEPROM

What else can I check from here please?
 
2informaticos

2informaticos

Administrator
Staff member
Check diode mode to ground on all secondary voltages.
Test the board alone on the desk.

Is the machine recognized in DFU mode?
 
overshoot

overshoot

Member
Yeah no, I already checked to see if the board was in recovery mode and it’s not.

The measurements are done with the board alone, out of the case.
 
2informaticos

2informaticos

Administrator
Staff member
All other M/SPMU LDOs are present?

If isn't recognized in DFU, you may have problems with CPU.

Just in case, compare diode mode readings around UF400/500 with good board.
Check their LDOs with charger alone.
 
overshoot

overshoot

Member
I do not have a working board for this model.
What if I am already getting 20V with the battery plugged in, does that rule out a CD3217 fault?

Also I can't get the machine to go DFU and trackpad won't click.
 
overshoot

overshoot

Member
I made some progress on this board and got it to DFU mode but it failed with 4042.
Following that, I've checked all the SSD rails and they were all present and steady for 30 secs, no prob.
Then I went back at it to measure some voltages and found something interesting.
The PPVOUT_KBDLED is sitting at 25V while the USB-C shows 5V at 0.1A.
So that doesn't right.
I went to replace UP800 which is the KB and LCD backlight chip and same thing.
Then I did the same with UP900 and no improvements.
I've checked all the diode mode values on those 2 chips and they all measure fine based on openboard data.
I have also noticed that PP3V3_AONSW_TPAD_ISNS is at 0.067V while the diode mode value is good at .410V
That coincides with what the customer gave me for symptoms of the Mac dying.
I've measured the diode mode values around UD300 and all is fine.

Any idea where else I can look from here please?
 
overshoot

overshoot

Member
Following down the rabbit hole, I went to check UT410 and the diode mode values are ok.
I am getting 0V at IPD_PWR_EN_GATE_R and 0V on pin 4 of UT480.
UT480 has good diode mode readings as well but 0V on IPD_PWR_EN which comes from the MPMU.

I need help from here please
 
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