2019 Macbook Pro A2141 / 820-01700-05 / No water Damage / Does not Boot / no DFU

[zeydullak]

I did a mistake. Sorry for that. The last reading was taken between the ground (screw hole) and coils. I will check diode mode testing between PPBUS_G3H and coils and post the results. Thank you.

 

[zeydullak]

Checked in diode mode with ohm scale --> Black Probe on PPBUS_G3H point --> F7000:2 and red probe on big coils. Please see the details. I do not see a 1 Ohm measurement which is direct short. Please kindly advise. If voltage injection is required, please give me a bit more details or just show me where to read on your forum. Thanks.

L8102 --> 67 Ohm
LA850 --> 70 Ohm
LA860 --> 67 Ohm
LA870 --> 68 Ohm
LA950 --> 65 Ohm

regards,
Zeyd

 

[2informaticos]

Is better to do same check against all coils.
This avoid any problems, if you need to inject voltage into PPBUS_G3H.

 

[zeydullak]

I checked all coils using a Siglent high accuracy multimeter. Please check the below results. All numbers in Ohms. Also, I have a working PCB and I am checking on that one, the number is generally 400-500 Ohms. Do you suspect something is shorted? Please advise how to proceed. Thanks.

L8410 --> 390
L8450 --> 485
L7030 --> 475
L7771 --> 108
L8102 --> 76
LA710 --> 40
LA720 --> 40
LA730 --> 40
LA740 --> 40
L7813 --> 899
L7817 --> 92
L7816 --> 91
L7814 --> 430
L7815 --> 430
L7821 --> 79
L7822 --> 79
L7806 --> 52
L7811 --> 68
L7812 --> 68
L7810 --> 700
L7600 --> 483
L7660 --> 552
L9030 --> 730
L9020 --> 144
L9021 --> 143
LA950 --> 70
LA850 --> 80
LA860 --> 71
LA870 --> 70
L7330 --> 53
L7231 --> 40
L7221 --> 40
L7211 --> 40
L7220 --> 43
L7410 --> 43
L9521 --> 152
L9520 --> 152
L9530 --> 134
L3500 --> 493
L7700 --> 486
LB700 --> 510

Regards,
Zeyd

 

[2informaticos]

Are these readings between each above coils and PPBUS_G3H?
In such case, is OK to inject voltage.

I understood you've checked on similar board.
But use diode mode and maintain same orientation for the probes.
Then you can compare the results.

 

[zeydullak]

I injected voltage into the PPBUS_G3H line and ground it to the screw hole. I started with 1v and it was using 400 mA. I increased the voltage to 2v and it was using 700 mA. Using IR cam, I saw that the area near U5620 is getting warmer. I applied some Isopropyl alcohol to understand the exact chip. It is a U9580 chip. I applied isopropyl several times and the u9580 chip is getting dried very fast. So this should be out shortly. Now going forward what next steps? I have not done anything yet. Should I remove that chip and check short again?

 

[2informaticos]

Ooops, bad news.

"Check if you get similar reading on any big coil; like L7600/60, L9080, L7701, etc..."
I've just saw you didn't put L9580 in "etc"; check it now.

 

[zeydullak]

L9580 - is 3 Ohm I missed it. Sorry.

 

[zeydullak]

I should be start looking near to the shorted area. The lack of experience. Let me know what you think about the 3 Ohm on L9580. Thanks.

 

[2informaticos]

Some NAND chip got burnt.
Remove L9580/81 and check where the short remains.

 

[zeydullak]

ok doing now.

 

[zeydullak]

I removed both coils. then I chceked continuity between PPBUS_G3H and L9581:1 (first pad), I receive 3 ohms again.

 

[zeydullak]

Now checked above listed coils against PPBUS_G3H, the numbers are between 3-7 Ohms. All of them show short.

 

[2informaticos]

U9580 is burnt also; it cuased NAND damage.
I was expecting diode mode to ground reading on pad 2/L9580...

We have another recent thread about similar problem:

820-01700-05 5V 0.00-0.01A on all USB-C Ports

If you are not afraid to change the NANDs chip, do it. You can't lose more than time now. I recommend to change U9580 and check its output before placing the new NANDs.

boards.rossmanngroup.com

 

[zeydullak]

diode mode to ground reading on pad 2/L9580 and 2/L9581 is 132 Ohm on both pads.

 

[2informaticos]

Compare reading with L9080/81.
May have luck, doesn't look to be short.
Change U9580 and check what happens.
Be sure all resistors and caps related with U9580 are good, before applying power!

BTW, diode mode, doesn't show ohm value!

 

[zeydullak]

Thank you very much. Please bear with me . I know I made mistakes and this is frustrating.

Diode Mode (Red Probe on ground) --> 2/L9580 and 2/L9581 is 0.111v. Please provide your comment about this as well.

Also "Be sure all resistors and caps related with U9580 are good, before applying power!". Can I check the resistors and caps while they are on the board? or I should remove them. Thanks.

 

[zeydullak]

Just rechecked in diode mode using my Siglent Multimeter and the result between ground point and 2/L9580 is 0.1322v. Much more precise number. Thanks.

 

[2informaticos]

Don't worry about precision; NAND should be good on both channels.
Need to change U9580 now.

Then you can also compare resistors value (in ohm), without removing from board.
Lucky enough to have two channels for comparison.

BTW, resistors with low ohm value will show almost same value.
High value resistors will show lower values than nominal, measured onboard.

 

[zeydullak]

I moved u9580 and also tested resistors. Then connected charger cable over USB-C meter. Now we have 20v and 290mA on the charger. Amper usage is not moving up. It stays at 290 Ma and then drops to 0 and again to 290mA. The normal boot process should use more power. Please advice. Thanks.