Homemade PSU for the C13 and C42 wireless sets


The original C13 power supply ,as you can see from the the schematic, was a DC powered
12V or 24V vibratory supply. These used reed vibrators connected as a synchronous rectifier. These days we would use a transistor inverter but the designers correctly thought that transistors in their day were not sufficiently powerfull or reliable. Vibrators were horribly inefficient, very noisy and in this instance resulted in DC saturation of the transformer cores. Regulation was just barely adaquate and the carrier tone from the transmitter portion had huge amounts of ripple and hum. When I bought my C13 from United Trade Sales ( remember them ?) with a collection of pocket money and birthday money, I handed over $35 dollars, was man handled a C13, was about to leave the shop when the nice  attendant said, and oh... you forgot this....  It was the seperate power unit. Just as well my friend Irving Gribbish came along that day, we both struggled up Swanston street to the train lugging these very heavy equipments onto the train. There were some strange looks.  I was able to acquire some of the power connectors , a British Armed Forces standard and all but unobtainable today and made a one to one power harness.

I was sufficiently disenchanted with the power unit, and not having a schematic was not in a position to improve it. Due it is high component density reverse engineering was out of the question. Instead I measured the power harness under various operating conditions and built a mains powered PSU from old television components to emulate its behaviour.  I had purchased the 12E1 bottle a year before for all of thirty cents. I thought the large surface area of the bottle and the large anode had to be usefull for something. Its still a favoured bottle for audio amp enthusiasts due to the very cathode current possible for this super cathode emission bottle.





The TV transformer DC raw supply had an open circuit voltage of about 700V DC peak so a seris pass regulator was required to drop it down to 150V as required by the main circuit. The regulation  was good and the resultant improvement in frequency stability caused me to use my C13 as a primary source of carrier, variable IF and frequency calibration for the rest of my ham radio activities.













This psu design can run the C13 and the C42 set simultaneously

Dont try to copy these design, they are more my notes than a cookbook design. these notes date from 1980 and beyond. If you must use solid state seris pass regulators look at the solid state drawing below, but use something more forgiving than a 2SD200, try a BUX80.







my tripe parallel seris pass 150 volt regulator made from old horizontal deflection bottles. The 47 ohm resistor in the anode circuits are required to prevent vhf parasitic oscillation. In fact the first pass of this regulator effectively prevented television reception in our neighborhood.





This unique solid state C42 PSU design by the Distinguished Mr Ian Holland
long time no see










The "Q" code by an early version of Mr Irving Gribbish, 1979
from Contronics Australia