I put a custom expansion board onto the nice T4-S3 devices' 2x15 header. But displaced by 1 pin (2 pins off) and shorted something out. Need help on how to troubleshoot and id the destroyed components.

Schematic:

https://github.com/Xinyuan-LilyGO/LilyGo-AMOLED-Series/blob/master/schematic/T4-S3-AMOLED.pdf

My initial troubleshooting results. Expansion board removed, display/touch-i2c removed, initial factory schematic connections. Connected via USB-C to power source/Laptop USB port.

1-. No USB tty device present. 2-. Activity LED is solid red. Normal device flashes continuously. 3-. VDD Power is a little low at 4.88VDC. 4-. VCC is very low...at 1.5VDC 5-. Powered off board resistance between VCC and GND is very low and symmetrical at 2.5 ohms. (Normal board this is much higher >20K if I remember correctly)

My initial thought was that the 3.3 power subsystem was fried. But I do not know, maybe it is just overloaded by a shorted out cap etc.

Apart from the USB/Battery/Serial-Port chip SY6970 https://www.electronics-lab.com/wp-content/uploads/2023/12/SY6970-.pdf, the only other major active component (display is removed) is the esp32 itself.

How can I debug and isolate the issue without having to remove (or only a few) SMT components?

I was thinking to somehow isolate everything and test the esp32 directly via it's rx/tx pins. Not sure if possible with the SY6970 connected.

Hoping the esp32 is still usable and the display interface logic. Do not need the USB or battery subsystems for my application. Have SMT solder station and can remove chips etc.