11-01-2018, 02:58 AM
(04-01-2018, 03:45 PM)Geordie McBoyne Wrote: "With hundreds of AC/DC radios & TV's only taking a half wave of each phase on a large circuit it must have upset the electric board a bit. What did they do about it?"
DC on the mains may have been less of an issue in the USA, with its split-phase supply system. With AC-DC receivers randomly connected to either side of a split-phase system, there would have been some net DC cancellation back at the centre-tapped secondaries of the supply transformers.
AC-DC radio receivers were I think quite common in the USA, and the standard valve range accommodated this with a 150 mA heater series. Also, there were quite a few valves, such as the 6BH6, 6BJ6, 6AQ6 and 12AT7 that could “swing both ways”. In the early 1960s, Sylvania introduced a range of 100 mA series-string radio valves for use in compact AM radio receivers.
American AC-DC TV receivers had something of a peak in the mid-1950s. In 1954, the industry introduced a range of 600 mA series-string TV valves with controlled heater warm-up times. In 1956 this was supplemented with a smaller range of 450 mA and 300 mA controlled heater warm-up time valves for use in the smaller and portable TV receivers. But I have read that some makers, after trying AC-DC TV receivers, reverted to the isolated type after a few seasons.
Cheers,
Steve
