A Power Supply for the T1154/R1155 (/cont)

6V DC Supply

A lot of current required …

According to A.P. 2548A, the LT dynamotor was designed to deliver 7V at 13A. The two VT104 pentodes in the T1154 draw 2.6A between them, the two VT105 triodes draw a further 2A (almost). The R1155 alone could draw up to 4.4A. All this doesn’t add up to 13A, but don’t forget that the 1200V dynamotor  was supplied from the LT dynamotor, as were the T/R relay and the HT supply interlock relay.

The diagram above is fairly crude. A simple rectifier and smoothing pack, a zener diode voltage reference and high-gain series regulator. Everything with the exception of the mains transformer came out of the ‘junk box’. The exact value of zener is set such that the on-load output voltage is as close to 6.3V as possible. I think it is in the region of 7.5V in this case. The actual value will depend on the nature of the series regulator.

See the photograph on the left …

RLA is bottom right. RLB, a genuine WW2 relay, is mounted on top of the chassis but the terminals can be at the seen bottom left.

The regulator and over-voltage protection circuit are on the tag-board.