This page is a stub article, but it is time to start gathering information about M1 repair practices. For now it is simply to throw things i learn during the repairs (i got 5 M1 macbooks which i cant repair but thats NOT a dead CPU / SSD, so i wont give up untill i fix them). DO not use it as a repair guide or reference of any time, i have probably no idea what i am talking about - @inwerp#2476
- There is no S5-S0 sequence anymore, Do not look for it, forget everything you knew about power rails, sequence. Finita. Like on T2, SSD is always powered on.
- The most important power rails now are 3v8 and 5v_S2. G3HOT is now called AON (Allways On?) -- Read below for more 5v_S2 info*
- If you have waterdamage and you need some ICs, stock donorboards. Go google AONE36196, thats a simple double mosFet with customized footrpint. I successfully substituted it with two standard N-fets for test purposes but thats not a repair.
- all CPU power rails are now generated with Apple proprietary PMU. This might be a good thing because you won really see high side-shorts to VCORE anymore. Bad thing, again - donor only.
- if you look at 13 inch logic board, there are WAY less chips and components compared to older devices.
- Backlight circuit is the same as on older models. Same LP8549/49 as described in this article
- wifi/bt module is a bliss. Check its fooprint and smile.
- For now 820-02020 is basically almost a development board. SV004. SV000, SV010, SC002 e.t.c are debug buttons. There are all sorts of resets, power button and force DFU on edge of the board, both sides. There are also debug leds which i plan to stock and test. Switching Fet , 6.8K 201 resister, LED 0201
While 5v_S2 is important power rail, it is not needed for the unit to power on. It seems to power several systems, but I have booted the board without UC300 (what generates 5v_S2). However this rail might damage lots of other components, specifically because feedback line consists of many 0201 resisters, failure of each one might cause ppbus on 5V rail which is high enough to kill all consumers at once and more of that, it causes failure of 3v8_aon generator (it has alternative VCC from 5V rail) which might be a complete disaster with both PMU failure and much worse, WLAN damage which is so far not replacable.
If you have any damage in UC300 area, do not power up to test the device, only test after you are 100% sure in feedback circuit.
Things powered by 5v_S2
- Display Backlight (directly powers LP8548)
- Keyboard Backlight
- Current sensing lines
- It looks like PP5V_SW_LCD is also powered by 5v_S2 by looking at schematics. However, when I had board booted without UC300, I did have image, just no backlight
as mentioned, 3v8_AON substitutes 3v3_g3h rail from previous modell, also partially thats similar to 3v_S5. It is enabled by CHGR_EN_MVR signal from ISL9240. It is mainly used by CPU Power IC / PMU (unlike 3v3_G3HOT it is a fat 3-phase power rail with buck converters and lots of caps).
Looks like all S2 Rails are enabled by PMU(U8100) itself, so power sequence would be something like:
Old CD3217-ISL9240 to PPBUS, + 3v8_AON, then PMU generates its internal LDOs, fires up S2 Rails. it is yet unknown if PMU is interchangable between Air/Pro boards, however it might be - most of enable signals are named GPIO on PMU.
P3V3S2 Line is used for auxillary components like Wifi/BT, sensors, switches.
5v_S2 is also important rail. It is generated by UC300(LT8642EV-2 Stepdown converter with integrated fet). If this rail is unstable, you will get all sorts of issues like weird 3v8 Rail (next rail to power up CPU PMU), blown backlight switch, etc. If any sign corrosion, check all surrounding area, especially Feedback circuit. Unlike many other power ICs we seen before, this one has 5 Resisters and 1 Capacitor on feedback line. 1 Corroded feedback and you have PPBUS on your 5vRail. Not good at all.
Possible damage from bad Feedback: UP700(Display power switch), U5700 (3v8 driver, there will be a very weird short 5V to Phase 3 low side gate which looks like hot Q5840 BUT some random voltage on L75840 ). As described in schematics, 3v8 Driver (U5700) might be powered from both PPBUS_VMAIN_VIN as well as PP5v_S2, so its overvoltage is quite dangerous for PMU and possibly CPU too.
Power Consumption during boot: 19v. 0.1-025 is a normal during POST / Boot phase. It also POSTS with 5V-1A if PD is disabled on USB Meter(weird but true).
- Turning on from battery only: connect battery, jump S5191, this will activate battery and keep it enabled, useful if you need data before you fix cd3217/TB circuit.
CPU/DRAM/NAND Resistance to ground (MacBook Pro 2020 M1 820-02020)
PP1V25_S2 5+kΩ, used both for CPU and CD3217 VDDIO Supply, so burned CD3217 with short on this line will almost definetely mean dead CPU.
PMU Master (U8100, provides main voltage rail to CPU)
PP5V_BSTLQ_VOUT_MPMU 10MΩ, internal LDO
Ths LDO is really important for AON Enable / IO system. Its absence/short will cause 5v 0A with 3v3 on 5v_S2 enable and few others (normal level is 1.8v). If shorted, check L8300(input filtering inductor)
PP1V2_S2 20MΩ+, external LDO for audio FPGA processor UR300
PP3v3_S2_UPC 40MΩ+ external LDO for CD3217 (substitutes 3V3_RTC on Intel models)
PP1V8_AON_MPMU 30KΩ+ external LDO used for few pullups and 1.8, 3v3 AON > LDO enables which are used for some SMC functions and communication lines pullups.
PMU Slave (U7700, provides voltages for RAM and few AUX supplies for CPU)
PP0V88_S1 10MΩ, internal LDO
PP5V_BSTLQ_VOUT_SPMU 10MΩ, internal LDO
Refer to old Backlight troubleshooting for most of possible issues. However, there is one weird thing to check: 1v8_AON rail is not critical for boot and start up but it is used for LID signal. If 1v8_AON is not present there will be communication between Backlight Drivers, there will be Boost and backlight enable signal. Looks like this was implemented that way so backlight voltage will be always present in S2 state for the famous "instant on" effect which turns backlight on with zero delay.
Compared to older models, LID trigger is way more complicated. It consists of many stages and powered by PP1v8_AON LDO (enabled by PMU itself). It is being generated from 3v8_AON rail by UC120 converter. It is very sensitive to any waterdamage on LID or overvoltage on 3v8 rail. It also worth to mention that AMR_RIGHT_OR_ND_1V8(located on audioboard) and AMR_LEFT_OR_ND_1V8(JR200 miniboard on main LB) are real LID signals from both HAL sensors.
Both signals are directly routed to UR300 FPGA chip which probably hardware-disables mic and camera once LID is closed. It also issues LID_OPEN signal sent to M1 SoC.
There is also UR200 OR gate which issues IPD_LID_OPEN_1V8 signal which is sent to Trackpad, Touchbar and PMU. So basically, this means that problems in LID circuit might cause no camera / microphone, no backlight but working touchbar and Trackpad haptic. Touchbar uses inverted signal (Low if "open"), most other circuits use high if "open".
Low PP1V8_AON (1.5 or 1.4v due to bad cap near regulator) would cause partial LID problems like disabled touchscreen on Toucbar, random no haptic click)
Tools and chips