mbcontrol
Member
I am working on a MacBook A3240 with logic board 820-03597-A.
Unfortunately I don't have a schematic or boardview for the 820-03597-A. I only have the schematic/boardview and OpenBoardData values for the similar 820-03286, so I am using that only as a reference and trying not to assume that the layouts are identical.
History:
The MacBook originally switched off after a few seconds and would not turn on again. Apple apparently performed a logic-board repair. The customer used it only 2–3 times afterwards and then the same failure occurred again.
Apple later returned it unrepaired and supplied a photo showing a ripped-off SMD inductor. I soldered the inductor back on, but the machine still does not start.
Current behavior:
Both USB-C ports behave almost identically:
Measurements so far:
VBUS reaches the USB-C controller at ~5.1V, but neither controller produces PPHV_INTx_AONSW, therefore PPDCIN_USBC_AON never comes up and consequently neither PPBUS_AON nor the downstream AON/S2 rails are established.
Both USB-C controllers showing almost exactly the same behavior makes me wonder whether there is a common missing prerequisite / bootstrap supply / enable signal, rather than two failed SN25A43 controllers.
On the 820-03286 reference schematic, the USB-C controllers also use PP3V3_S2_LDO, PP1V25_S2 and PP1V8_S2, but all of these are currently missing on this board. I am trying to determine which rails/signals must already exist during the initial 5V cold-start phase and which are only generated afterwards.
Does anyone know the SN25A43 cold-start sequence, or which rail/signal I should check next before suspecting the USB-C controllers themselves?
In particular, I would be interested in experience with 820-03597-A / A3240, or any information about the bootstrap supplies/enable conditions required for the SN25A43 to pass the initial 5V input towards PPDCIN_USBC_AON.
Thanks!
Unfortunately I don't have a schematic or boardview for the 820-03597-A. I only have the schematic/boardview and OpenBoardData values for the similar 820-03286, so I am using that only as a reference and trying not to assume that the layouts are identical.
History:
The MacBook originally switched off after a few seconds and would not turn on again. Apple apparently performed a logic-board repair. The customer used it only 2–3 times afterwards and then the same failure occurred again.
Apple later returned it unrepaired and supplied a photo showing a ripped-off SMD inductor. I soldered the inductor back on, but the machine still does not start.
Current behavior:
Both USB-C ports behave almost identically:
- USB-C 0: 5V, approx. 178mA
- USB-C 1: 5V, approx. 180mA
- No negotiation to 20V
- Current is stable
Measurements so far:
- PPVBUS_USBC1: 5.095V
- PPVBUS_USBC1 diode mode: 0.177V (OBD reference from 820-03286: 0.153V)
- PPHV_INT0_AONSW: 0V
- PPHV_INT1_AONSW: 0V
- PPHV_INT5_AONSW: 0V
- PPDCIN_USBC_AON: 0V
- PPDCIN_USBC_AON diode mode: 0.590V (03286 reference approx. 0.567V)
- Fuses between the PPHV/PPDCIN rails have continuity
- PPBUS_AON: 0V currently (I measured approx. 0.6V once yesterday, but this is not reproducible)
- PPBUS_AON resistance to GND: approx. 2.5MΩ
- PP3V8_AON: 0V
- PP3V3_UPC0_LDO: 1.667V
- PP3V3_UPC1_LDO: 1.95V
- PP1V8_UPC0_LDO: 0V
- PP1V8_UPC1_LDO: 0V
- PP3V3_S2_LDO: approx. 0V
- PP1V25_S2: 0V
- PP1V8_S2: 0V
- CHGR_SYS_5V: 0V
- PP5V_CHGR_SW: 0V
- PPCHGR_VDDA: 0V
- PPCHGR_VDDP: 0V
- PP5V_S2: 0V
VBUS reaches the USB-C controller at ~5.1V, but neither controller produces PPHV_INTx_AONSW, therefore PPDCIN_USBC_AON never comes up and consequently neither PPBUS_AON nor the downstream AON/S2 rails are established.
Both USB-C controllers showing almost exactly the same behavior makes me wonder whether there is a common missing prerequisite / bootstrap supply / enable signal, rather than two failed SN25A43 controllers.
On the 820-03286 reference schematic, the USB-C controllers also use PP3V3_S2_LDO, PP1V25_S2 and PP1V8_S2, but all of these are currently missing on this board. I am trying to determine which rails/signals must already exist during the initial 5V cold-start phase and which are only generated afterwards.
Does anyone know the SN25A43 cold-start sequence, or which rail/signal I should check next before suspecting the USB-C controllers themselves?
In particular, I would be interested in experience with 820-03597-A / A3240, or any information about the bootstrap supplies/enable conditions required for the SN25A43 to pass the initial 5V input towards PPDCIN_USBC_AON.
Thanks!