Battery valve filaments - UK Vintage Radio Repair and Restoration Discussion Forum

Herald1360 · 10th Nov 2017, 6:44 pm

Slightly odd question:

Is there any convention as to which pins of a B4 based triode (like PM1HF etc) are F+ and F-?

I suspect it doesn't actually matter as long as the grid bias is referred to whichever is used as F-, but I'd like to know....

kalee20 · 10th Nov 2017, 8:17 pm

Doubt it.

Some valves, like the DAF91 it could be critical, as the diode anode is located at one end of the filament. And I suppose that for optimum design, the grid-cathode spacing (or the grid wire pitch) could be varied to compensate for the potential gradient along the filament. But in the B4-based days, I can't see that level of sophistication being incorporated.

10th Nov 2017, 6:44 pm	#1
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Battery valve filaments Slightly odd question: Is there any convention as to which pins of a B4 based triode (like PM1HF etc) are F+ and F-? I suspect it doesn't actually matter as long as the grid bias is referred to whichever is used as F-, but I'd like to know.... __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

10th Nov 2017, 8:17 pm	#2
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,081	Re: Battery valve filaments Doubt it. Some valves, like the DAF91 it could be critical, as the diode anode is located at one end of the filament. And I suppose that for optimum design, the grid-cathode spacing (or the grid wire pitch) could be varied to compensate for the potential gradient along the filament. But in the B4-based days, I can't see that level of sophistication being incorporated.