Accidental short on logic board

Hi, I wanted to flash DeMux on my machine to fix discrete GPU problems.

Unluckily I did not think (…) about disconnecting the battery cable before soldering the JTAG header on the board, and one of the wires did some short somewhere on the board (I heard the “zap”).

Now:

machine does not turn on

battery button does nothing

Plugging magsafe only does a **very** dim green light.

Is there a walk-through guide on what to check in this case?