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Old 13th Feb 2018, 7:46 pm   #7
Alf Fisher
Hexode
 
Join Date: Sep 2005
Location: Potton, Bedfordshire, UK.
Posts: 292
Default Re: When did Valve heaters change from 4v to 6.3v

Hi dragonser,
Way back in the 1960s, I bought a GEC AVC5 radio from a scouts jumble sale for 5 bob. It dates from 1934 and had a lineup of valves X30, W30, DH30 and N30 which all had 13 volts heaters. The rectifier was a MU14 which was 4 volts. It sounds like your transformer could have come from one of these sets.
Regarding when 6.3volt valves came into service, I suspect it happened gradually in the mid-late 1930s. Some manufacturers stuck with 4 volt valves using tried and tested designs but it all changed when American octal based valves appeared in the receivers of the day and European valve manufacturers had a range of side contact valves that also came with 6.3 volt heaters.
This might have arisen from the developing car radio market as many cars had 6 volt batteries but I could be wrong!

Alf
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