Dave the whole thing was working on the day I took it! even the projector, it was from a government building that had been sold off and was getting stripped out the guys working there didn't want it, I got in touch with the collector and we just took it all away he didn't need the power amps as he already had some whose casings were better but I doubt if they were as original as the ones I've got. The plate voltage can come down a lot from 1200V though you lose output, mine have a B+ of around 450V so about 4W audio output. I haven't fired them up for a few years but one day I'll drag them and the other stuff I've collected out into the open and get them going again. The old van I had at the time wasn't big enough to get that thing into it so we strapped it onto the roof and drove 30 miles to where this guy lived. I got about $200 for the horn and the projector
though that was the same as 4 weeks wages back then as a 1st year apprentice gas engineer!