26-04-2018, 04:17 PM
Presumably the designers did some work on tolerances and reckoned that overrunning or underruning the heaters didn't matter too much in that application. One presumes the valves were worked well witin their capabilities, not like a CRT or a line output valve which was often being pushed somewhat. Also the relationship between emission and heater voltage is far from linear. I don't know the actual law but if it's like filament lamps then 20% overvoltage will increase the emission (and shorten the life) by several times more than 10% overvoltage.
That said, Terry is sensible to err on the side of caution, especially as new valves will get increasingly scarce,
That said, Terry is sensible to err on the side of caution, especially as new valves will get increasingly scarce,
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
