Hello
I have the above radio but it is missing the voltage reg tube,could anyone tell me about this tube and is it really necessary.
If it is where could I purchase one.
Thank you
Joe

This tube's function was to compensate for voltage fluctuations in the AC line. AC line voltage regulation was poor when the set was made, so at the time this was a useful feature to protect the expensive tubes in the set from a voltage surge. This feature is no longer needed for most people who get their power from The Grid. You can replace the tube with a power resistor but you will need to calculate its value and power rating.

You can do this by connecting the transformer line side up to a Variac that is set to minimum output voltage. Put an AC voltmeter across either of the 25 ohm resistors on the tube-heater output windings and SLOWLY increase the Variac setting until you achieve the correct filament voltage reading (note: all tubes need to be in place in order to provide the correct current load). The RMS voltage reading that you want is 2.5V. When you achieve 2.5V, shut off the Variac and look at its dial. Presumably it will be somewhat less than actual line voltage- maybe 100 volts or so. Now set up your meter for AC current and put the meter in series with the Variac (don't touch its setting). Turn the Variac back on and wait for the set to warm up, then capture the AC current reading. The voltage drop (actual line voltage minus Variac setting) and the set's current draw will let you calculate the needed ohmic value of the dropping resistor, and you can figure out its required power rating by the following formula: 2xLineCurrentxLineCurrentxResistance.

It may be possible to operate the set with the regulator tube bypassed, but I suspect that this will overheat the transformer since it is probably designed to operate at a lower voltage and current (i.e., with the ballast tube in place).

:This tube's function was to compensate for voltage fluctuations in the AC line. AC line voltage regulation was poor when the set was made, so at the time this was a useful feature to protect the expensive tubes in the set from a voltage surge. This feature is no longer needed for most people who get their power from The Grid. You can replace the tube with a power resistor but you will need to calculate its value and power rating.
:
:You can do this by connecting the transformer line side up to a Variac that is set to minimum output voltage. Put an AC voltmeter across either of the 25 ohm resistors on the tube-heater output windings and SLOWLY increase the Variac setting until you achieve the correct filament voltage reading (note: all tubes need to be in place in order to provide the correct current load). The RMS voltage reading that you want is 2.5V. When you achieve 2.5V, shut off the Variac and look at its dial. Presumably it will be somewhat less than actual line voltage- maybe 100 volts or so. Now set up your meter for AC current and put the meter in series with the Variac (don't touch its setting). Turn the Variac back on and wait for the set to warm up, then capture the AC current reading. The voltage drop (actual line voltage minus Variac setting) and the set's current draw will let you calculate the needed ohmic value of the dropping resistor, and you can figure out its required power rating by the following formula: 2xLineCurrentxLineCurrentxResistance.
:
:It may be possible to operate the set with the regulator tube bypassed, but I suspect that this will overheat the transformer since it is probably designed to operate at a lower voltage and current (i.e., with the ballast tube in place).
:

Jacobi's ballast tube handbook lists the D-110 for 30V drop and 1100ma current.
Carl T

Thank you for your reply,
This set may have to sit for a while until I get the the required equipment or tube.
Thank you again,
Regards joe