I'm just wondering if anywhere in the UK was still DC by the time TV arrived? If so, a tiny minority of likely sales. My home town of Aberdeen changed from DC to AC in the 1930s, and it was getting on for 20 years before TV got that far.
ISTR some hybrid sets - part valve part transistor - that still used a dropper for the valve side, but a more normal transformer for the low volts transistor side.
Were they also maybe designed for export to Commonwealth/Empire countries?
A quick check on the web suggests some time in the 1960s - so well after BBC and ITV were on the air.
It is ironic that most of our present electronic equipment could work quite well on DC mains.
I guess.
PA
Parts of Nottingham were until the late 1950's
P represented a heater current of 0.3Amp and U 0.1Amp.
The later valve sets would generally have two half wave rectifiers, negative one driving the heater chain and the other smoothed by caps for the HT.
Also as a general rule the CRT cathode would have the lowest heater voltage, or should I say closest to Neutral.
I would expect the Line Output Efficiency Diode to be the most rugged and at the hottest end of the heater chain and the line output PL81/PL36 next?
Many chassis were at Neutral potential. When rules came about the DC content of AC some chassis were at a pseudo mid-potential but still dangerous.
All external controls would be through plastic or other insulating material. I think I saw audio isolating transformers where there was a headphone socket to overcome the live chassis issue.
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I think that production of the older, Universal design was extended by:
a) it was a cheap approach, b) it was there for both AC and DC, and, c) there was a very big rental market in those days - and the rental companies wanted cheap sets to rent out.
PA
Only if the plug and socket were both wired correctly.
What about the aerial wires? It was only separated from the chassis by an inadequately related ceramic capacity, usually.
They were generally 1nF, but I guess would have the necessary voltage rating in its time. There were stories of aerials being live from a failure but never actually came across a failure.
'rated'!
Only if the plug was correctly wired. And given the time, plenty two pin non polarised sockets still in use.
Tell me about it. My worst shock was from a US radio with a dropper wire in the mains cable using obscure colours and a 'live' chassis.
It couldn't happen now !!
Our Potterton bo1ler's electronics is referenced to the Line, rather than the Neutral.
God knows why.
PA
Seen that more then the once. There is or was rather the Aerial Isolator unit this was a panel where the aerial was coupled via a couple of well rated capacitors and a high value leakage resistor to remove static charges from the aerial in thundery weather.
It was usual for the socket to get damaged by pulling on the aerial cable so the socket would be bypassed! Set would work OK but if the mains plug was arse about face then aerial is now at full mains potential.
Unsuspecting aerial rigger on reaching the aerial reaches out, one hand on his roof ladder the other now around the aerial pole nice 'hin't it!!
The time i had to do aerial work I'd brush the back of my hand across the pole a strong "fuzz" feeling usually meant down tools, aerial out set unplugged etc!...
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