For this months tube presentation I picked another TV damper tube from my collection. The 12D4.
The 12D4 is equivalent to the 6DA4, except it uses a 12V heater. The 6DA4 was already presented in a previous tube of the month post.
The 12D4 uses the same pinout as all other TV dampers. The heater voltage is 12.6V and it consumes 0.6A of current. For the complete technical data refer to the RCA data sheet. While TV dampers with 6.3V heater slightly increased in price during the recent years, versions with different heater voltages can be picked up very cheaply. I stocked up many 12V, 17V, 19V and 22V heater TV dampers just in case supplies of 6.3V types dry up. But although it is more widely known now that TV dampers make excellent rectifiers in tube amplifiers they are still available in abundance. For more background information about TV dampers, read the tube of the month post about the 6AU4. Let's look at some of the 12D4 tubes from my collection, starting with RCA:
Next we have a more modern RCA 12D4 with a so called coin base:
A coin base Sylvania 12D4:
Hoffman branded 12D4:
International Service Master:
That's all about the 12D4!