[Milsurplus] Looking for info: ARC/38 250kHz PTO (Collins 147A-1)

[Ian Wilson]

I have figured out the power connector (not difficult, since there
are only 3 leads <g>). The submini tube filaments light OK.

However, the unit doesn't oscillate. There is some internal diode
switching that seems to be related to the INPUT (a mini coax connector).

Any suggestions for what needs to connect to INPUT (or better, a schematic)
would be helpful. The OUTPUT connector pin connects via a 470k
resistor to one of the PTO coil terminals. Doesn't 470k seem high for an
output connection?

I've looked at the Collins 618-S manual but the circuitry around the
250kHz BFO is not very similar to what I see in this PTO.

73, ian K3IMW