I had the same issue with my Randall RM100. It ended up being blown fuse. I think it was an internal filament fuse but it's been a while and can't remember exactly.
I don't know what a Windsor has for fuses, but it wouldn't hurt to check. Make sure to test continuity with a meter. On my Randall fuses visually looked intact. It wasn't until I put them on the meter that I found the blown one.