Blowing fuses T4 SCR Drive

Blowing the F11 Fuse. I took the wire off the interface board and the fuse held. Put the wire back on it blew again. At term 16 I'm reading dead short. Found it at the end of the day. Tomorrow ill be trying to isolate more wires off the board to see if the ground is coming into the board from another wire or the board is grounded itself. Any suggestions? Only spent 15 mins with it. Ill be back on her tomorrow.

You'd never guess what caused the fuse to blow, the f11 fuse feeds 120v to the control interface board, that fuse blows you have no drive. Well off the interface board the fans for the drive are wired into it. Grounded fan. Very odd design.

Schindler did this on their Miconic VM product. The drive logic power supply (120VAC as well) also fed the drive fan below the drive SCR bank and on the top of the controller. Really had my head scratching as to the 'logic' on that design. There is also a fan airflow switch, and I would have thought using it would have been a more elegant method of pulling the car out of the service at the end of the run rather than during.

They are not on prints, have had that before

The fan is on my print and off the same fuse that feeds power supply #1. I had that fuse blowing recently and thought (hoped) it was the fan, but it turned out to be the power supply.