820-02016 Strange Problem

[brunomotter]

Hello. Got this one here, which I'm thinking may have a NAND problem. It does not turn on, don't negotiate 20V with charger, BUT, after taking some measurements and inspecting the board a little under the microscope I found that PP2V5_AWAKE_NAND is around 3.5V oscillating and UN100 gets a little warm. Charger stays at 5V and takes 0.42A from charger. Some caps around UN100 were bad and I replaced them, but still same symptom. If I take RN430 the board power cycles, going to 20V, trying to turn on and shuts off, cycling. I'm suspecting bad UN100, but who knows...

 

[2informaticos]

2V5_AWAKE_NAND comes from L7760.
Check R770C and its traces (XW7760).
If good, then bad U7700.

Just in case, check ohm resistance between L7760 and 3V8_AON rail.
When RN430 is removed, what's 2V5_AWAKE_NAND voltage?

 

[brunomotter]

2V5_AWAKE_NAND is 3.5˜3,6V with or without RN430. Traces and R770C are good, bad U7700. No repair for this one then as I don't have any donor boards from this model.

 

[2informaticos]

PMUs from M1 14" and 16" are compatible.