UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - When did Valve heaters change from 4v to 6.3v

turretslug · 14th Feb 2018, 12:07 am

I wonder if the 4V to 5V rectifier trend was more a case of following US practice for commercial reasons than any particularly technical motive? As mentioned upstream, a pre-war trend that rapidly became a general theme as the US became the Allies' industrial power-house and innumerable 5Z4 etc. were available, perhaps. The US adoption of 2.5V and 5V filaments/heaters for many valves before 6.3V became widespread is worthy of questions itself though.... My understanding of the 6X5/EZ35 early adoption of 6.3V and isolated heater/cathode was for car radio power pack use- but that's both hazy and tenuous!

14th Feb 2018, 12:07 am	#11
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,400	Re: When did Valve heaters change from 4v to 6.3v I wonder if the 4V to 5V rectifier trend was more a case of following US practice for commercial reasons than any particularly technical motive? As mentioned upstream, a pre-war trend that rapidly became a general theme as the US became the Allies' industrial power-house and innumerable 5Z4 etc. were available, perhaps. The US adoption of 2.5V and 5V filaments/heaters for many valves before 6.3V became widespread is worthy of questions itself though.... My understanding of the 6X5/EZ35 early adoption of 6.3V and isolated heater/cathode was for car radio power pack use- but that's both hazy and tenuous!