820-01700 - No power - 20V 0.8A

[ronaldopdias]

Hi.
Got this Mac to repair which has no signs of liquid. No previous history.
Battery is dead, but I tested with a good working battery and still same.
PPBUS_G3 - 12.7V
PP3V3_G3H_RTC - 3.38V
PP1V8_SLPS2R - 1.8V Cycling.
T2 is glowing from one side and cycling.
SLPS2 and Awake is all cycling.

• LDO0: 0.8V Cycling
• LDO1: 3.0V Cycling
• LDO2: 1.2V Cycling
• LDO3: 1.8V ~ 1.78V
• LDO_RTC: 1.5V Stable
• VOUT_RTC: 3.3V ~ 2.69V
• LDO_CORE: 1.5V

I've checked all the coils in diode mode and all seems fine.
U7800 replaced an same issue.
Revive gets stuck on Installing system.
Do you think the T2 ic itself is faulty or it still could be software?

In DFU mode before staring Revive option all the power lines mentioned above are stable.
As soon as I press Revive or Restore it starts to cycle again.

Thanks

[sajidmirza]

I RECOMMEND U TO FIRST CHK ALL THE CD3217 CHIPS AND COMPONENTS AROUND IT,THEN ALSO CHK U7000 CHIP AND COMPONENTS AROUND.

[ugamazing]

Check SSD voltage and inspect for liquid to the power supplies. Common failure on these.

[ronaldopdias]

I replaced the NANDs, CD3217 all 4 and the U7000 and it still same issue.
Do you think by any change the problem would be on the PCH?
I could just replace, but I don't have the stencil for this.

[ugamazing]

With T2 cycling and glowing, it's probably the culprit in this case. Just wanted to confirm the SSD wasn't the culprit, but now you've confirmed: Bad T2. You can replace it, but you'll need an unlocked donor etc. Also need to make sure you replace with identical model T2 (confirm part number--NOT just pulled from another 01700 as they're not all identical).

[mon2]

Does PPBUS_G3 - 12.7V not imply that the T2 has booted and is working?

[ronaldopdias]

T2 replaced and the issue still there. Same symptoms.

[ugamazing]

Does PPBUS_G3 - 12.7V not imply that the T2 has booted and is working?

I took his "glowing on one side" comment as a T2 short, as that's not a usual thermal print for that chip (and if it's rails are cycling but it *still* heats up quickly enough to catch via thermal?). But yes if ppbus is stable then T2 may actually be fine, but damn what's left? Bad CPU/GPU on these rarely prevents DFU/restore, and he's replaced SSD/T2/PMU/ACEs. Maybe a continuity fault? Maybe start checking your rails on all areas of the board just to be sure, maybe it was bent at some point?

[mon2]

Remove all power. Meter in resistance mode.

What is the exact resistance of the following?

PP3V3_G3H_T @ L7660.

LDO0
LDO1
LDO2

[ronaldopdias]

• LDO0: 0.195
• LDO1: 0.452
• LDO2: 0.528
• LDO3: 0.610
• LDO_RTC: 0.378
• VOUT_RTC: 0.391
• LDO_CORE: 0.376
• PP3V3_G3H_T @ L7660: 0.392

[mon2]

What scale was used on the meter?

what are the units of measurement?

resistance was requested.

[ronaldopdias]

The T2 that I replaced is from same lb model. But I just realize that the original T2 from the board I'm trying to fix is
h9hknnnBRumuvr-nlh and the donor T2 is
h9hknnn8Kumuvr-nlh.

Both board has 1TB storage.
Is this relevant?
Thanks.

[ugamazing]

The important number will be the part number, i.e. "339S00467" etc. They MUST MATCH or the board won't power/boot/restore/etc. I believe on the 01700 2.3/1TB boards, they are largely the same but different RAM configurations will use different chips. For boards like the 00850, they had TONS of different T2 chips--maybe 10 or so. Super critical to match part numbers or you'll go crazy.