A1708 820-00840 Intermittently Not Detecting SSD - Question Mark - Previous Liquid Damage

[it-solve]

It turns on and works fine for a while, but often when it starts or awakes from a long-term not usage turns on with a question mark. Same when used for an extended period of time.

Previous liquid damage around U3890/5 doesn't seem to be related to SSD lines. Also, some around R3773 and U3700 corner.

Tested with two good known SSDs, reinstalled still an intermittent issue. Cant measure with a board outside of the case when an issue occurs hence omitted some measurements.

J8600 - When Problem Occurs
4 - 0.24V
5 - 0.003V - SSD_PWR_EN_CONN_L
6 - 1.78V - SSD_BOOT_CONN_L
7 -
8 - 0V
9 - 3.4V
10 - 3.2V
11 -
12 -
13 - 3.2V

Looking at @tipoti trouble when it's working, measurements seem to be the same as mine when not working.

Cleaned the connector multiple times and inspected under a scope. No damage.

 

[2informaticos]

If no changes on signal and control lines, then should be a communication problem on data lines.
You should test with external USB macOS and check if internal SSD is still detected in Disk Utility, but you can't access it to read/write.

 

[it-solve]

When I reboot usually comes online and works as expected. I can load from it, and it runs perfectly with no SSD errors. Haven't seen it come with a question mark again after I shut down and rebooted from the previous question mark. It loads up straight away until the next time when it crashes and reboots to a question mark.

Just from time to time comes with a question mark and an error after a restart - your mac restarted because of a problem.

 

[2informaticos]

There should be some corroded contacts, traces, or data line components...