It is built into a big black wood cabinet with a vented enclosure sitting in the bottom and this is also made out of black wood although it was never seen. We decided the black wood was too good to leave this box inside the unit and if I ever get round to restoring it I will make a craft wood version of this enclosure complete with its 12 inch speaker. The original record/payback arm has been broken and replaced with a rather poor home made item. In a box inside the unit was the original broken arm and a replacement, complete with the mechanism that moves the arm accross the surface of the record.
The rubber suspension isolators that supported the motor were broken and the motor was dangling on the end of its wires. The original Isolators were half inch by half inch with a 3/8th inch BSF thread stud growing out of each end. The only ones I can buy now are the same dimentions but the threads are 3/8th Whitworth. Not a problem, there is enough metal around the original fine thread to tap them 3/8 Whitworth. Take the front off the motor first as the windings are quite close to the holes in the front. The part number is Mackay M160.
The story is this monster was in the Adelaide Town Hall for many years and was used to record concerts. So far I have found a user manual for the BRS Junior Recorder and Playback Unit type R-12-D from this web site and there is information about the tape unit also: Australian Professional Audio Equipment
Head for Manufacturers, Byer Industries and then look at Disc Cutter, Byer R-12-D and Tape Machines, Magnofilm.
The serial numbers of the parts are: the TM1 s/n 193 and the R-12-D s/n 410
This thing has got me curious so I spent last night looking at the BIG chassis and taking it apart.
It had been extensively modified/rewired/butchered at least thirty five years ago by the components used.
The output stage is push pull 6V6 in a strange direct coupled configuration, not too sure the if whoever worked on it last got it correct. Have not put the scribbled bits of paper together in one circuit diagram yet.
Uses a cascade phase splitter that was direct coupled to the grids of the 6V6 but can?t see what they did to jack the cathodes up so the tubes had bias.
Anyone got any circuit that looks like this in your head ??? May have used the second power supply !
When I start on something like this I have a pile of half A4 scrap paper sheets I draw each area as a mechanical diagram, rather than a circuit and then one day I work out what it looks like as a circuit.
The original rectifiers were a pair of 5Y3 (evidence, 5 Volt heater windings on both transformers), but these had been replaced with a mess of early silicon diodes and wire wound resistors.
The nice A and R transformer is not original, would be 10 to 15 years younger (evidence the holes in the chassis). The two things I thought were both chokes are in fact another power transformer and a choke. The rubber leads on these were rotten but when I took them apart I found they were terminated on the edge of the winding in lugs and so they now have cloth covered replica wire leads.
The P-P 6V6 is the suggested drive configuration for the cutter head (from the information on the APAE web site) driven off the two anodes via ?leaky? 2uF oil filled caps. I hope I can find the original circuit for this portion of the cutter Amp as the front end obviously has compensation circuitry but someone has been at that and replaced octal valves in here with an EF86 and a 12AU7. These tubes would not have been used in the late 1940's when it was origially built.
Put it away for a few weeks now, got other things to do. Would like a sunny warm day to clean and paint the chassis. Will not take long to put it all back together but I would like to know more about the original circuit configuration.