[ARC5] Filament Question

[AKLDGUY .]

The little battery tubes such as the 1T4 and 3S4 were designed
to run from carbon batteries, which have significant internal
resistance. In the heater circuit, the cell's internal resistance
provides sufficient inrush current limiting, IMO.

If you intend to run the heaters from a carbon cell, well and
good. If you want to use a transformer, especially one that has
low winding resistance and capable of supplying far more current
than the heaters draw, you better include a switchable resistor to
act as inrush limiter, IMO.

73 de Neil ZL1ANM