Macbook Failures From Experience
This page is more of a diary of repairs, more than a guide on how to repair.
820-00958 CPU Failure
The unit came in with slight liquid damage on U7650, U6940, and Q7660. Shorted was PP5V_G3S. The shorted component was U8245. After replacing U8245, I found that PP5V_G3S was 10v, instead of the 5v that it was intended for. After only a few seconds of having the board on again after replacing U8245, to check measurements, it was shorted again. At this point, I replaced U7650, Q7660, and repaired several traces and capacitors, resistors. Once again, replacing U8245. This time when powering on the board PP5V_G3S, was at its normal voltage. However, the unit still would not boot. Hovering about 20v 100mA. So after further investigation, I found PPVCCIN_AUX_PCH was not being generated. This was due to PPVCCINAUX_VCC being shorted to ground. This failed component was U7400. Which was powered by PP5V_G3S. So, after replacing U7400, I was making progress. The unit would start the boot process, getting 1v8 on PPVCC_S0_CPU for a second, then 0v, but pulsing. So on/off/on/off scenario. I found the pulsing started all the way back at PP1v8_SLPS2R. I did find, however, that if I removed R7210, R7220, and R7230 the system would be stable again. These are the three resistors that powers PPVCC_S0_CPU. At this point, I am pretty certain that I have some sort of CPU failure. Wether it be the CPU itself or not, I am not sure. I felt that it was, as I have a suspicion the 10v going through the CPU MOSFETs probably killed the CPU. However, as a last desperation, and for research, I decided to attempt to DFU the machine. At his point, it failed, and I got error code 9. This was somewhat expected, as all the power rails are pulsing currently. So what I decided to do, was remove the three resistors mentioned early, to make the system stable again. At this point, the DFU restore went through successfully. This leads me to believe that CPU failure can cause error code 9
820-01700 Not booting without battery, not charging stone dead battery
Unit not booting without battery present. This board will boot on a 96watt adapter normally. I have seen 3 cases where the board doesn't boot on the adapter alone, and wouldn't charge a stone dead battery normally.
Without battery connected: 20v with a jump to 300-500mA then back to 70mA and kind of sit there.
With battery connected: It would very slowly raise to charging amperage. (It would take 2 to 3 minutes for it to reach 4 and a half amps, vs the normal 30 seconds to a minute)
After diagnosing the charging circuit, and seemingly everything on the board is physically okay, I decided to DFU restore the unit, thinking something with the SMC, that T2 is now handling.
This resolved the issue.
820-00928 PPBUS not being generated, no shorts
5v and 100mA for about 10 seconds then would jump to 20v 60mA - PPBUS not being generated. Initially found short on SMBUS_SMC_5_G3_SDA caused by D6950. After diode replacement, same result. Resolved issue by replacing SMC.
Voltages I had
- PPBUS_G3H - 0.300
- PP3V3_G3H - 3.4
- TBA_GATE_Q1 - 0
- TBA_GATE_Q2 - 0
- TBA_GATE_Q3 - 0
- TBA_GATE_Q4 - 0
- PPVIN_G3H_P3V3G3H - 19.8
- TBA_AUX_DET - 5.07
- HPWR_EN_L - 3.36
- SMC_RESET_L - 3.4
- TBA_VDDA - 5.07
- TBA_VDDP - 5.07
- PM_EN_P3V3_G3H - 5.08
- PPDCIN_G3H_CHGR - 19.8
- SMC_BC_ACOK - 3.4
- CHGR_AMON - 0
- CHGR_BMON - 0
820-01949 PPBUS Short, leading to T2 shorted
This one started with 5v-60mA, classic PPBUS short draw for the T2 models. The PPBUS short was caused by U6903. After removing the IC, PPBUS short went away, however after probing the area around, I discovered PP3V3_G3H_RTC was short as well. So before I injected any voltage I removed R5920, which connects PP3V3_G3H_RTC to PP3v3_G3H_SSD. Probing under this resistor, I found that the short on PP3V3_G3H_RTC went away, and PP3V3_G3H_SSD0 was shorted. This time the short was caused by U9000. So after replacing U9000 and U6903 I checked around both ICs for shorts and didn't find anything. So I went ahead and attempted to boot the unit. At which point the unit would just restart my amp meter repeatedly, before even giving me a reading. All the power rails were pulsing from PPBUS to 12.6v to 3v very rapidly, and the pulsing stopped at PP3v3_G3H, which was just 0v. At this point I discovered that PP1V8_SLPS2R was shorted. The short being caused by T2. Just speculating, but I think something that connects PP3V3_G3H_RTC and PP1V8_SLPS2R probably shorted internally, and shoved 3v3 into 1v8. Again, purely speculation.