There was a time following the Second World War when TV sets for the nascent broadcast medium were still very expensive, but there was an ample supply of ... black-and-white CRT TV from a kit ...

[GK] spends most of the time so far talking about the high voltage power supply design. For the particular tubes he had on hand he needed +200V, -400V, -550V, and 6.3VAC for the CRT heater.