16-08-2021, 04:27 PM
Since P series valves are usually cheap and readily available it makes sense to arrange heater supplies for them. There are a few that are false friends. ISTR that PL84 is not the same basic valve as EL84.
A thought. If you wanted to use a PL84 instead of a UL84 you would need to ensure that any other valves in the 100mA chain were not overrun. I reckon a 4uF motor run capacitor would supply about 300mA to the PL84 heater. All sorts of other possibilities with transformer windings, rectifiers with smoothing, diode droppers or cap droppers.
A thought. If you wanted to use a PL84 instead of a UL84 you would need to ensure that any other valves in the 100mA chain were not overrun. I reckon a 4uF motor run capacitor would supply about 300mA to the PL84 heater. All sorts of other possibilities with transformer windings, rectifiers with smoothing, diode droppers or cap droppers.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
