Homemade PSU for the C13 and C42 wireless sets
These notes originate from 1976 when I was still in high school,
so that might explain the choice of components; that and limited pocket
money and the fact that nearly all my component supply came from
discarded all valve TV sets.
The original C13 power supply ,as you can see from the the schematics,
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 ( Londsdale st ,
Melbourne .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.