01-14-2023, 10:09 AM
I know that this is an old thread but:
- The B+ values are common.
- You should be able to find a new transformer with at least one 2.5V winding in addition to the 5V and HV windings.
- For the 24A filaments, a center tap is not really needed. one leg of that winding can be grounded.
- If a transformer with a center tap for the 45 filament can't be found, an "artificial" tap can be made by putting 2 10 Ohm resistors in
series. The Junction is the center tap. Note that the current drawn by these 2 resistors (125mA) has to be accounted for when sizing
the resistors and the winding.
- In at least one radio I found (A Studebaker 31 TRF Radio (for 115V AC), all tubes are powered by the same winding. the winding is -
center tapped and the center tap is grounded through a 500Ohm resistor and 0.5uF capacitor to provide the bias necessary for the 47
tube.
- A power transformer from a Philco 70 would provide all windings and voltages needed.
- If really desperate and if only a non-tapped secondary for 2.5V tubes is available and you find the 22 10 Ohm resistors to not -
work, convert the 45 to a 2A5. It is not too hard. However, if this is the "Peter Pan" model, nothing other than the original
transformer will do, to protect the value of the radio.
- The B+ values are common.
- You should be able to find a new transformer with at least one 2.5V winding in addition to the 5V and HV windings.
- For the 24A filaments, a center tap is not really needed. one leg of that winding can be grounded.
- If a transformer with a center tap for the 45 filament can't be found, an "artificial" tap can be made by putting 2 10 Ohm resistors in
series. The Junction is the center tap. Note that the current drawn by these 2 resistors (125mA) has to be accounted for when sizing
the resistors and the winding.
- In at least one radio I found (A Studebaker 31 TRF Radio (for 115V AC), all tubes are powered by the same winding. the winding is -
center tapped and the center tap is grounded through a 500Ohm resistor and 0.5uF capacitor to provide the bias necessary for the 47
tube.
- A power transformer from a Philco 70 would provide all windings and voltages needed.
- If really desperate and if only a non-tapped secondary for 2.5V tubes is available and you find the 22 10 Ohm resistors to not -
work, convert the 45 to a 2A5. It is not too hard. However, if this is the "Peter Pan" model, nothing other than the original
transformer will do, to protect the value of the radio.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55