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A2251 820-01949-A
- Thread starter hgoncalves
- Start date
Check SSD coils in diode mode to ground.
hgoncalves
Active member
HI,
L9020/21 = 0.388
L9030 = 0.362
L9080/81 = 0.151
L9020/21 = 0.388
L9030 = 0.362
L9080/81 = 0.151
"L9080/81 = 0.151"
Compare with good board; looks low...
Compare with good board; looks low...
hgoncalves
Active member
I don't have any other a2251board to compare it.
Is there any other way to be sure?
Is there any other way to be sure?
hgoncalves
Active member
Hi.
Thanks for the OpenBoardData Project.
I think I've made a mistake, and measured PP2V5_NAND_SSD0 when it was hot, because right now I have the correct value there : 0.410 on diode reading, and 2.5V.
Any other idea?
Thanks for the OpenBoardData Project.
I think I've made a mistake, and measured PP2V5_NAND_SSD0 when it was hot, because right now I have the correct value there : 0.410 on diode reading, and 2.5V.
Any other idea?
Erase SoC ROM and try again DFU restore.
Make a backup first.
Make a backup first.
hgoncalves
Active member
Hi.
After erasing SoC ROM U4770, the mac now stays at 5V and isn't recognized in DFU.
However, I have a strange behavier: now I only have again 0.136 diode reading on PP2V5_NAND_SSD0.
Sometimes I get the corrrect value, and other times I don't.
Any idea? Can I inject 2V there when I have a wrong reading there?
After erasing SoC ROM U4770, the mac now stays at 5V and isn't recognized in DFU.
However, I have a strange behavier: now I only have again 0.136 diode reading on PP2V5_NAND_SSD0.
Sometimes I get the corrrect value, and other times I don't.
Any idea? Can I inject 2V there when I have a wrong reading there?
Last edited:
Always allow 10-15s after power is removed, before checking in diode mode, or ohm scale.
hgoncalves
Active member
OK. tks.
After erasing SoC ROM U4770, the mac now stays at 5V and isn't recognized in DFU.
Shall I restore it?
After erasing SoC ROM U4770, the mac now stays at 5V and isn't recognized in DFU.
Shall I restore it?
Erasing SoC ROM should put MLB directly into DFU.
hgoncalves
Active member
Hi.
Still stuck at 5V and not recognized in DFU.
PPBUS_G3H = 12.28V
PPDCIN_G3H is 5V
PP3V3_G3H is 3.3V
U3100_X diode readings:
PP3V3_UPC_X_LDO = 0.506
PP1V5_UPC_LDO_CORE_X = 0.529
USBC_X_CC1 = 0.585
USBC_X_CC2 = 0.583
U3100_T diode readings:
PP3V3_UPC_T_LDO = 0.501
PP1V5_UPC_LDO_CORE_T = 0.525
USBC_T_CC1 = 0.572
USBC_T_CC2 = 0.571
U3100_R diode readings:
PP3V3_UPC_R_LDO = 0.510
PP1V5_UPC_LDO_CORE_R = 0.527
USBC_R_CC1 = 0.572
USBC_R_CC2 = 0.570
U3100_W diode readings:
PP3V3_UPC_W_LDO = 0.501
PP1V5_UPC_LDO_CORE_W = 0.527
USBC_W_CC1 = 0.593
USBC_W_CC2 = 0.591
Still stuck at 5V and not recognized in DFU.
PPBUS_G3H = 12.28V
PPDCIN_G3H is 5V
PP3V3_G3H is 3.3V
U3100_X diode readings:
PP3V3_UPC_X_LDO = 0.506
PP1V5_UPC_LDO_CORE_X = 0.529
USBC_X_CC1 = 0.585
USBC_X_CC2 = 0.583
U3100_T diode readings:
PP3V3_UPC_T_LDO = 0.501
PP1V5_UPC_LDO_CORE_T = 0.525
USBC_T_CC1 = 0.572
USBC_T_CC2 = 0.571
U3100_R diode readings:
PP3V3_UPC_R_LDO = 0.510
PP1V5_UPC_LDO_CORE_R = 0.527
USBC_R_CC1 = 0.572
USBC_R_CC2 = 0.570
U3100_W diode readings:
PP3V3_UPC_W_LDO = 0.501
PP1V5_UPC_LDO_CORE_W = 0.527
USBC_W_CC1 = 0.593
USBC_W_CC2 = 0.591
Machine should be recognized in DFU mode.
Recheck what you did on the board.
Recheck what you did on the board.
hgoncalves
Active member
Hi.
I've just erased U4770.
Nothing seams to be wrong on that area.
Everithing is in place, and I can't see nothing wrong.
I've just erased U4770.
Nothing seams to be wrong on that area.
Everithing is in place, and I can't see nothing wrong.
If machine was recognized before in DFU mode, something happened when you worked on it.
So check for knocked off components, damaged traces, or connectors.
So check for knocked off components, damaged traces, or connectors.
hgoncalves
Active member
DFU Mode Restore (Macs) - LogiWiki
We have Apple MacBook and iPhone Diode readings and general fault finding information compiled by the leaders in this area
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