[MrFixr55]

Hi SRv2,

What you need depends on the type of farm set. There were many different versions including the following:

2V A (filament), 90V or 135V B, -3, -7,5V C for many farm sets from about 1932-1938

1.5V A, 90V B some farm sets from mid 1938 on, many battery only portables

6VDC (Set used a vibrator power supply for B+, tube heaters and the vibrator power supply ran off 6VDC from a storage battery, much like a car radio). Common on farms that were mechanized or had windmills (Win-Charger)

32VDC (series filament string, and space charge tubes that could run off 32VDC without a vibrator power supply. These were used on farms that had a 32V power plant and bank of storage batteries.

If the set uses 1.5V for A and 90V for B, consider using a D Cell for the A battery and the circuit from Phil's Old radios for a B supply. However, use an isolation transformer with that supply. The supply that Rod B built is excellent and is likely much cheaper to build than buying an ARBE

The ARBEIII is expensive but could run the first 2 types easily. I have one and love it, but I use it for the old 1920s sets that use 01As, 112s, 71s, etc. Of the 3 commercially built supplies that you researched, the ARBE is head and shoulders above the others, especially considering the price of the others. At $140, I wouldn't even consider the BEAR.

For my RCA 5BT and 6BT (2V, 135V, -3, -7.5V, I built a 135V supply for about $50. For the 2V filaments, I used a 3V 1A wall wart and a 2 Ohm 5 W resistor (the set needed 2V at 500 mA for the heaters).

Hope this helps.