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Customer says that the screen went out, then it stopped chiming. I tested the screen and it was missing its backlight (I replaced the 49B1-04 backlight chip on the T-con board and the screen works now). I only have data on the big coils from a similar model (A2159, 820-01598), do you have exact...

This 2020 A2289 board shows 20V on USB-C, pulling 0.05A-0.16A. No liquid damage. I have PPBUS at 12.6V (dropping to 12.3 every 20s or so) and the SLP, AWAKE, and G3S rails are all present. No obvious shorts on the big coils. SSD rails are all there. CPU area gets mildly warm but not hot. I...

Success! I found that one of the right speaker amps was also liquid damaged (UR760). Replacement restored sound on speakers. Apparently, all 6 amps must be functional for speaker audio. Incidentally, do you know which speaker amps (A-C, D-F) correspond to what frequency ranges? Thanks.

Both measure 0.32 in diode mode and 1.2V in voltage mode. No shorts there. Correction: I do get sound through headphones now, just not the speakers.

This machine was exposed to liquid and would not start up. It initially presented with corroded left speaker amps, a shorted backlight driver UP800, as well as liquid-damaged trackpad. After cleaning and replacement of speaker amps UR660/UR630/UR600 and UP800 the machine is functional except...

I got the port to work by replacing JE701. A pin must have been bent and not made contact.

Diode mode readings are identical between the two USB ports. I forgot to mention that along with the three CD3217s, I had to replace UF650 due to a short on PP3V3_S2_LDO.

This 820-02536 came in with 2 of 3 CD3217s shorted. I replaced all 3 CD3217s from a donor board, along with the 2 TBT ROM chips (U5560, UF260). Now the machine is fully functional except for the data line on USB port 1. Charging works on this port and it provides external 5V, just does not mount...

It’s still the same cycling as I wrote earlier. Both are steady for a few seconds (12.3 and 3.8) until the charger resets and all rails dip to zero.

If I can't find any shorts on any secondary power rails, why are the PMUs cycling on and off? How do I find out why the charger resets?

All pins on UD200 measure good - identical to a known good board. On battery power alone, the AON rails (PPBUS, PP3V8, PP1V8, PP3V3) are steady but all other power rails cycle (turn off every second).

With a battery connected, PPBUS stays at 11.6V. When I plug in a charger, PPBUS cycles between 11.6 and 12.3V.

The battery connector was internally shorted. Removal of the connector removed the short. Now onto getting a new connector and back to testing with a good battery.

I just found out that PPVBAT_AON_CONN is 15Ω to ground. When I inject 3V into PPVBAT_AON_CONN, the only thing getting warm is the CPU. Does that make any sense?

Unfortunately I don't have a charged battery or a functional A2681. Anything else you would check?

I did and nothing changed at all. The battery could be empty though. I need to verify on another A2681 machine.

All LDOs for both PMUs are there, some briefly, some steady.

PPBUS and 3V8 are steady for a few seconds, until the power resets and all rails dip to zero. Need to check the LDOs.

This 820-02536 presented with areas of liquid damage in the R_SPKRAMP area near UN000. I removed two corroded caps that had shorted PPBUS_AON and PP1V25_AWAKE_NAND to ground. Now, connecting a charger gets PPBUS of 12.3V and 5.1 on USB-C. The charger gets to 20V but as soon as it does, the...

All tests were done with battery connected; that's how I found out that the board restarts with every plug/unplug of the charger cable. PPBUS is 12.3V, then as the Apple logo shows it drops to 12.0V. The startup process is interrupted by either USB-C resetting spontaneously, or by unplugging...