Simple Filament Soft Start
Simple Delayed B+
Start with a separate 6.3VAC secondary (use it to power a rectifier, and not any other tubes).
Connect a 5Y3 5V 2A filament in series with a 0.65 Ohm resistor, across the dedicated 6.3V secondary.
The cold 5Y3 filament is about 0.6 or 0.7 Ohm, so it starts to warm up with only about 3.15V across it.
It takes a long time for the 5Y3 to warm up.
Type 80 shoulder tube rectifiers look real pretty. Same 5V 2A filament rating as the 5Y3.
Apply the same principle to your favorite Direct Heated Filament tube (just recalculate according to the filament rating, and needed excess secondary voltage to get the job done).
Many of my old transformers have "6.3V" secondaries that are actually closer to 6.8V.
All my input tubes and output tubes have a series resistor to give 6.3V across the filaments when they are fully warmed up.
Simple Delayed B+
Start with a separate 6.3VAC secondary (use it to power a rectifier, and not any other tubes).
Connect a 5Y3 5V 2A filament in series with a 0.65 Ohm resistor, across the dedicated 6.3V secondary.
The cold 5Y3 filament is about 0.6 or 0.7 Ohm, so it starts to warm up with only about 3.15V across it.
It takes a long time for the 5Y3 to warm up.
Type 80 shoulder tube rectifiers look real pretty. Same 5V 2A filament rating as the 5Y3.
Apply the same principle to your favorite Direct Heated Filament tube (just recalculate according to the filament rating, and needed excess secondary voltage to get the job done).
Many of my old transformers have "6.3V" secondaries that are actually closer to 6.8V.
All my input tubes and output tubes have a series resistor to give 6.3V across the filaments when they are fully warmed up.
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