I think there is a transistor driving the LED on the A3K, its probably gone open circuit, find the transistor and change it.
I have to say Ive been lucky as Ive shorted most of my Amiga's against the case one way or another and after an hour max the machine turns on and is fine, guess Ive just been lucky
EDIT----
Ok after looking it was a 7407 and it was resistor protected.
But it seems they didnt protect the 5V power.
it goes 5V+ ---- LED ---- resistor ---- 7407 chip.
So if you shorted the 5V to ground then it was a direct short, check if the PSU is outputting 5V still and then check a chip to see if its getting 5V.
There is no fuse protecting the main 5V line from what I can see.
