Hello everyone,
About me, my goal and the equipment I (don't) have:
I am brand new to this forum, and I am eager to learn about repairing laptops. I have an engineer background although I haven't done electronics for a while. I have watched several Youtube videos in the last two months, trying to understand how to diagnose a faulty motherboard. I have a USB-C Amp meter and a classic multi meter. No DC Power Supply to inject voltage, no soldering iron to replace components.
About my issue and my goal:
A friend of mine has a MacBook Air M1 A2337 that does not power on. He went to an Apple Store which told him to change the motherboard. He bought another laptop, and gave me this faulty MacBook so I can have fun trying to repair it. As I want to learn, this is a perfect exercise for me. I am here to share what I have done until now on this MacBook, and ask for help to continue my diagnosis. Once the diagnosis is completed, I want to ask someone to replace the faulty part for me. My goal is to understand what to do to continue the diagnosis.
This being said, now the fun part!
Troubleshooting process:
Hardware: MacBook Air A 2337 (M1, 2020). Board number 820-02016.
History: No liquid damage, no drop, nothing particular. It just stopped powering on one day, after a complete discharge. It had only 3 years of use. My friend kept it in a closet until I ask him to give it to me 3 weeks ago.
In these 3 weeks I have run the following tests:
- Measured power in the 2 USB-C ports, in both directions. It gave me 5.1V, and random A, some bursts at 0.430A, then around 0.05A, then another burst at 0.430A.
- Opened the laptop, removed the motherboard, and did my first voltage measurements on motherboard ever:
Then, I looked in the schematics to look for what the PPBUS_5VS2_VIN is feeding. I found that UC300 is supposed to create PP5V_S2 from PPBUS_5VS2_VIN. As PP5V_S2 is missing, I want to see if P5VS2_EN is different from 0V.
Also, I search the Internet, and found this resource: https://repair.wiki/w/MacBook_Pro_A2...w_at_5V_repair
This resource says to check PP3v3_S2 voltage at LC710, which is at the output of UC710.
So, I did another round of measurements:
I notice that I have no PP3V3_S2 signal, although UC710 is enabled and that I have a PPBUS_3V3S2_VIN signal.
This is where I am stuck.
I think the next step is to look for short-circuits. But I am not sure where, and how to do that. I have measured continuity between GND and LC710 (both sides), and my multi-meter does not beep. Resistance is very high between these two spots. Also, I have measured PP3V3_S2 in diode mode (red probe on GND, black probe at LC710), and it gave me 0.257. I don't know how to interpret this value.
I interpret this situation as follows: there is no short-circuit. If there were a short, I would have had less than 1 Ohm between LC710 and ground. Is that right?
If I had found a short, I would have tried voltage injection and alcohol/freeze spray/thermal camera to find the shorted component. But now I do not know what to do. My guess is that it is the UC710 that is faulty and need to be replaced. But I am not sure at all of my diagnosis.
Also, I don't understand why one of the CD3217 has created its LDOs, and the other has not. If UC710 were faulty, I would have expected all LDOs not to be created. How do I know that the faulty component is not one of the two CD3217?
What do you think of my analysis so far, and what would you do now if you were me?
Any help or link to useful resources to help me understand would be really appreciated!
Cheers,
mkdj
About me, my goal and the equipment I (don't) have:
I am brand new to this forum, and I am eager to learn about repairing laptops. I have an engineer background although I haven't done electronics for a while. I have watched several Youtube videos in the last two months, trying to understand how to diagnose a faulty motherboard. I have a USB-C Amp meter and a classic multi meter. No DC Power Supply to inject voltage, no soldering iron to replace components.
About my issue and my goal:
A friend of mine has a MacBook Air M1 A2337 that does not power on. He went to an Apple Store which told him to change the motherboard. He bought another laptop, and gave me this faulty MacBook so I can have fun trying to repair it. As I want to learn, this is a perfect exercise for me. I am here to share what I have done until now on this MacBook, and ask for help to continue my diagnosis. Once the diagnosis is completed, I want to ask someone to replace the faulty part for me. My goal is to understand what to do to continue the diagnosis.
This being said, now the fun part!
Troubleshooting process:
Hardware: MacBook Air A 2337 (M1, 2020). Board number 820-02016.
History: No liquid damage, no drop, nothing particular. It just stopped powering on one day, after a complete discharge. It had only 3 years of use. My friend kept it in a closet until I ask him to give it to me 3 weeks ago.
In these 3 weeks I have run the following tests:
- Measured power in the 2 USB-C ports, in both directions. It gave me 5.1V, and random A, some bursts at 0.430A, then around 0.05A, then another burst at 0.430A.
- Opened the laptop, removed the motherboard, and did my first voltage measurements on motherboard ever:
| Signal name | Measuring spot | Values | |
| PPVBUS_USBC0 | CF401 | Not measured | |
| PPHV_INT0_AONSW | FF200 | Fluctuates between 4.86 and 5.18V | |
| PPHV_INT1_AONSW | FF201 | Fluctuates between 4.86 and 5.18V | |
| PPDCIN_AONSW | FF200 (aussi) | Fluctuates between 4.86 and 5.18V | |
| PPBUS_AON | F5200 | Fluctuates between 11.9 and 12.3V | |
| PP1V8_S2 | CF403 | Fluctuates between 0 and 0.135V | |
| PP5V_S2 | CP941 | 0V stable | |
| PP1V25_S2 | C5320 | Fluctuates between 0.09 and 0.13V | |
| PP1V2_S2 | C830A | Fluctuates between 0 and 0.70V | |
| PP3V3_S2_UPC | RF283 | Fluctuates between 0 and 0.134V | |
| PP1V8_AON_MPMU | R8324 | 1.8V stable | |
| MPMU_VREF_ADC | C8321 | 0V stable | |
| USBC0_3V3LDO_EN | TPG087 | Fluctuates between 0 and 0.02V | |
| USBC0_3V3LDO_EN_R | RF012 | Fluctuates between 0 and 0.002V | |
| USBC1_3V3LDO_EN_R | RF112 or TPG063 | 0V stable | |
| PPBUS_5VS2_VIN | CC325 | Before removing the board, with AC adapted and battery plugged in: fluctuates between 10 and 12V and I hear a "clic" in the battery every second After removing the board : fluctuates between 12 and 12.3V, and I don't hear any "clic" |
|
| PP1V5_UPC0_LDO_CORE | CF405 | Fluctuates between 0.05 and 0.16V | |
| PP3V3_UPC0_LDO | CF408 | Fluctuates between 0.65 and 0.82V | |
| PP1V5_UPC1_LDO_CORE | CF505 | 1.586V stable | |
| PP3V3_UPC1_LDO | CF508 | 3.44V stable | |
| PP3V8_AON_VDDMAIN | CF110 | 3.79V stable |
Also, I search the Internet, and found this resource: https://repair.wiki/w/MacBook_Pro_A2...w_at_5V_repair
This resource says to check PP3v3_S2 voltage at LC710, which is at the output of UC710.
So, I did another round of measurements:
| Signal | Measuring spot | Values | |
| PP5V_S2 | LC320 | 0V | |
| P5VS2_EN | PPC210 | 0V | |
| PP3V3_S2 | LC710 | 0V | |
| PPBUS_3V3S2_VIN | CC721 | 12,3V stable | |
| P3V3S2_EN | PPC200 | 1,57V stable | |
| PPBUS_5VS2_VIN (extra measurement) | CC325 | 12,3V stable | |
| PP3V3_S2 (diode) | LC710 | 0.257 | |
| P3V3S2_PGOOD | PPC201 | 0V |
This is where I am stuck.
I think the next step is to look for short-circuits. But I am not sure where, and how to do that. I have measured continuity between GND and LC710 (both sides), and my multi-meter does not beep. Resistance is very high between these two spots. Also, I have measured PP3V3_S2 in diode mode (red probe on GND, black probe at LC710), and it gave me 0.257. I don't know how to interpret this value.
I interpret this situation as follows: there is no short-circuit. If there were a short, I would have had less than 1 Ohm between LC710 and ground. Is that right?
If I had found a short, I would have tried voltage injection and alcohol/freeze spray/thermal camera to find the shorted component. But now I do not know what to do. My guess is that it is the UC710 that is faulty and need to be replaced. But I am not sure at all of my diagnosis.
Also, I don't understand why one of the CD3217 has created its LDOs, and the other has not. If UC710 were faulty, I would have expected all LDOs not to be created. How do I know that the faulty component is not one of the two CD3217?
What do you think of my analysis so far, and what would you do now if you were me?
Any help or link to useful resources to help me understand would be really appreciated!
Cheers,
mkdj
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