820-00850 No Power

hello dudes! got an interesting board here. 820-00850 board. had short to GND on L7660. injected 1V there and found a shorted cap C7895. removed and short gone. board still does not power on. some ports take 20V, some 5V, no other shorts. no liquid damage. when 20V on charger, I get around 2V on F7000 and 0.01A power draw, when 5V on charger I get 12.24V on F7000(?!?!?!) and 0A draw. I found that PPVRTC is not being generated. Any hints on what to look? The board is absolutely clean, no corrosion anywhere nor any signs of liquid, it was almost even dust free. I'm lost now! Thanks in advance
 

2informaticos

Administrator
Staff member
You should get same behavior on all USB-C ports first.
Specify how each port reacts.
Do not connect battery, nor other device, apart of charger.
Remove USB-C ports from the shell and clean their pins.
 
Here we go:

Right Side Closer to LCD: 5V, 0A
Right Side Closer to Keyboard: 19.5V 0.01A

Left Side Closer to LCD: 5V, 0A
Left Side Closer to Keyboard: 19.5V 0.01A
 
U3200:

PP1V1_UPC_XB_LDO_BMC - 0.466
PP1V8_UPC_XB_LDOD - 0.450
PP1V8_UPC_XB_LDOA - 0.484
PP3V3_UPC_XB_LDO - 0.474

U3100:
PP1V1_UPC_XA_LDO_BMC - 0.463
PP1V8_UPC_XA_LDOD - 0.445
PP1V8_UPC_XA_LDOA - 0.480
PP3V3_UPC_XA_LDO - 0.472

UB300:
PP1V1_UPC_TA_LDO_BMC - 0.470
PP1V8_UPC_TA_LDOD - 0.454
PP1V8_UPC_TA_LDOA - 0.488
PP3V3_UPC_TA_LDO - 0.474

UB400:
PP1V1_UPC_TB_LDO_BMC - 0.470
PP1V8_UPC_TB_LDOD - 0.452
PP1V8_UPC_TB_LDOA - 0.487
PP3V3_UPC_TB_LDO - 0.476
 
Here we go:

U3100:

PP1V1_UPC_XA_LDO_BMC - 1.115V

U3200:

PP1V1_UPC_XB_LDO_BMC - 0V

UB300:

PP1V1_UPC_TA_LDO_BMC - 0V

UB400:

PP1V1_UPC_TB_LDO_BMC - 1.116V


This board is acting very strange! I left it sitting in my bench yesterday when I went home and today the ports start behaving differently, now sometimes ports that would not negotiate 19.5V negotiate and sometimes not and the ports that would negotiate 19.5V started to intermittently not negotiate... Strange!
 

2informaticos

Administrator
Staff member
Very strange values.
Looks like the board switches to 20V only on the ports where you do NOT get 1V1 LDO; are you sure about the measurments?
Please check again and post accurate information.
To switch at 20V, SMC must work and communicate with corresponding CD3215 chip.
That is impossible without PPBUS_G3H, needed to generate 3V3_G3H.
 
This board is REALLY strange.... Sometimes the same port that was negotiating 20V suddenly starts negotiating 5V and vice-versa... I cannot get it to stabilize.
 
It's very weird here! Got back working on this board and now it's even more bizarre than before. When any port gives me 20V, F7000 gives me around 2.1V dropping and R7020 gives me 0V, when it negotiates 5V with charger I have 12.26V on F7000 and R7020 gives 5.18V...
 

2informaticos

Administrator
Staff member
Be sure to make good contacts when you measure on the board.
To switch to 20V, corresponding CD3215 chip MUST talk with T2.
This imply PPBUS_G3H, 3V3_G3H and more T2 voltages (SLPS2R, AWAKE).
Be sure to use original Apple charger.
 
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