K8000 assembly

Just dusted off my K8000 board, I made it a few years ago and never got it working, not even plugged into my PC.
On taking a closer inspection i had realised that i had plugged in IC24 (6N136) upside-down. I reorientated this plugged to the mains and now I now measure between 15v and 22v from the 5v test pin.

Does anyone have any idea what i have done horribly wrong?

Thanks

Roy

Looks like the +5V regulator is not working (e.g. shorted or defective).
Most likely, all IC’s that run from this +5V will be destroyed.