A1708 820-00840-A no power

[2try’s]

Hi, this is my first post here.
I have a board that not powering on. This Mac had problems with backlight flex, but after changing it and testing it refused to power on. I don’t think that flex caused this problem, guess it’s shorted somewhere or something

Board takes 5v around 0.030A from usb-c charger.

PPBUS_G3H - 0.014v
PP3V3_G3H - 3.404v
PPDCIN_G3H - 5.268v
3v3 and 5v s5 is missing

I have this board for quite a long time and I have already tried to change cd3215’s, u2800, u5000 and reball u3900, u4000 so maybe it’s my fault
I guess this was useless but I had much less experience and still learning

 

[2informaticos]

First of all, welcome to the forum!

If machine was booting before repairing the flexgate issue, then you did something wrong in the process.
Possible broken trace, knocked off components, damaged some connector.
After changing and reballing so many components, board is maybe trash.

Remove F7000 and check C7050 voltage.
Test the board alone on the desk.

 

[2try’s]

Thank you for your reply

C7050 voltage - 0.007v

 

[2informaticos]

So you have a problem on U7000 area.
Post its basic voltages: P_IN, AUX_DET, SMC_RST_IN, VDDA/P, EN_VR1, SMC_RST*, AUX_OK, A/BMON.

 

[2try’s]

PPDCIN_G3H - 5.269v
TBA_AUX_DET - 1.321v
SMC_RST_IN - 0v
TBA_VDDA - 5.054v
TBA_VDDP - 5.054v
PM_EN_P3V3_G3H - 5.054v
SMC_RESET_R_L - 3.409v
SMC_AUX_OK - 3.409v
CHRG_AMON - 0.003v
CHRG_BMON - 0.002v

All of this voltages are pulsing between this values and lower voltages (5.269 to 4.5 or 3.7, or something like that for every rail I mentioned)

 

[2informaticos]

"PP3V3_G3H - 3.404v
PPDCIN_G3H - 5.268v"
You didn't mention any fluctuation on the first post.
What is actual behavior of these two voltages?

USB-C meter restarts?

 

[2try’s]

I will send exact values tomorrow when ill get to the office

Usb-c meter didn’t restart but pulsing between 26-32mA
Sorry that didn’t mention it in first post

 

[2try’s]

PPDCIN_G3H - 5.269 pulsing 3.8v, 4.9v, 4.7v, 4.6v etc., not stable
PP3V3_G3H - 3.403 pulsing 3.3v, 2.1v, 2.0v, 3.2v etc., not stable
It pulsing once every 5 sec+-

 

[2informaticos]

5V on input fuses also pulsing?

 

[2try’s]

What do you mean? Where should I check it?

 

[2informaticos]

F3000/10, depending which port the charger is connected.

 

[2try’s]

F3000 - 5.276v, sometimes pulsing between 5.265-5.279

 

[2informaticos]

Didn't check what happens when connect the charger on the other port???

 

[2try’s]

Both connectors acting the same

 

[2informaticos]

So both F3000/10 have steady 3.2V?
R7020 voltage fluctuates in both cases?

 

[2try’s]

with minimal pulsing but yes, F3000/10 is 5.2v steady (not 3.2v)
And yes, R7020 voltage is fluctuating in both cases

 

[2informaticos]

Then you should have problems with U/Q3100/200.

 

[2try’s]

Just tried to replace both of u3100/200 and q3100/200 but it have the same results

 

[2informaticos]

Check U3100/200 LDOs; diode mode to ground and voltage too.

 

[2try’s]

Just noticed that u2800 is shorted, i dont have any to change, but when I plugged in a charger without this chip, tester showed 20v 133mA