But seriously, using plywood as the insulation material for a ( high impedance) valve circuit is a very poor idea - cos wood is hydroscopic.
Once the wood absorbs even a small amount of moisture from the air - the material will become conductive, resulting in serious bias shifts all over the place and maybe producing cracking & squealing noises in the audio output.
I have seen this actually happen when someone decided to rewire a modern "Fender" guitar amp using a hard grey cardboard with solder studs and solid wire in place of the original fibreglass PCB. The problem proved near impossible to fix.
Original Fenders used a similar technique - but Fender had the sense to fully impregnate their cardboard with hot wax beforehand.
kind of like a matrix board, it's not printed on the back (so not a _printed_ circuit board, just a support for the components), look how the wires are terminated on rings of copper. dry cellulose is a good insulator.
I think that's got three motors, like the black one on the fifth row.
Definitely plywood, you can see the layers on the edge, but it looks like discrete wiring not printed. Ok I suppose if it is dry and well lacquered, the heat from the tubes should help keep it dry. There is a guy in Canberra who makes expensive tube amps, he uses wooden strips with brass screws as tag strips.
It probably uses high grade Burmese plywood needles :)
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