This was a mobile amp that was somewhat common back around the late 1970's. It used a single 8417 tube (similar to a 6L6, but much higher output), and a pair of chopper transistors with a toroidal transformer to generate the high voltage. This is a grid driven amp, using a variable transformer input / 50 ohm swamping resistor to maintain a 50 ohm input, and a link coupled output. They work pretty good with a QRP rig on 10m, and would provide about 100w output on SSB, 50w on CW, and about 35 watts carrier on AM. The DC-DC converter in amps like this is noisy, but you could stuff it under the seat or in the trunk and it all was well.
This one originally had TO-3 style PNP germanium switchers. They had failed (not uncommon on this model) and damaged some wiring when that happened. I drilled the heat sink for a pair of much heavier TO-36 devices, capable of handling much higher current values and better heat dissipation. The flex cable from the center pole of the relay is what switched heavy current for the power supply, and had also failed. I replaced it with a heavy piece of copper braid, as well as a few capacitors were replaced.
