Converting From 6 Volt To 12 Volt

 The process I have used in the past is to replace all the tubes with the 12 volt equivalent and rewire the power transformer primary winding for 12 volt. The rewinding is replacing the wire with wire that has 1/2 the cross sectional area and wind twice as many turns to maintain the correct turns ratio. So, if the original wire is 17 AWG and 70 turns, the new winding would be 20 AWG and 140 turns.

One gotcha I have encountered is that the 6C4 tube has no 12 volt equivalent. There are few solutions to this and some research is in order:

1. Pin for pin 12 volt version (most desirable) - Unobtainium
2. Not pin for pin, rewire socket (12BF6)
3. Make an adapter 7 pin to 9 pin and use 1/2 of 12AU7 (µ=17)
4. Replace 7 pin socket with a 9 pin and use 1/2 of a 12AU7
5. Leave two 6 volt tubes and connect their filaments in series (filament currents must be close)

I'll post on antiquesradios.com forum to get more ideas.

Potential equivalents:

EC90
6135
M8080
6100
6AB4
6DR4

Tubes in the radio:

Actual Tube     12 Volt Equiv.

6BA6 (2)          12BA6

6BE6 (1)          12BE6

6AV6 (1)          12AV6

6C4  (1)          ???? <<<<<<<<

6AQ5 (2)          12AQ5

6X4  (1)          12X4

Rewire socket and use a 12BF6 with diode plates grounded????

Filament Currents

6BA6   0.3 A

6BE6   0.3 A

6AV6   0.3 A

6C4    0.15 A

6AQ5   0.45 A    

6X4    0.6 A