You need a 6-V power supply, preferably rated at least 2A continuous. The battery-eliminator kit sold by AES is rated at only 1.5A (on the A supply), and would be very dicey and the regulator would get quite hot. The ARBEiii is rated 3A, and would be OK, except it costs $139 + S&H. If you intend to get into 1920s battery-powered TRFs, this would be a nice bench supply.
You can shop around for a dedicated 6-V power supply or build your own. Another approach is to get a small 6-V wet cell with a small charger.
Your radio would not have run on dry cells -- which wouldn't have lasted very long before they were shot. It would have used a 6-V wet cell (lead-acid). The idea was to haul the wet cell into town and get it recharged periodically, or maybe use a wind charger?
:A have aquired a philco 38-39, 6 volt dc model.
:What would be the best way to drop 120 volts ac to 6 volts dc and get the same performance (or better) as the old dry cell?
For the B supply, simply purchase one of Radio Shack's 400 volt full wave rectifiers. Connect the AC input of the rectifier to the AC cord of the filament supply. Connect the negative output of the rectifier to the radio's chassis, and the positive to where the original power transformer's center tap connected. Disconnect the original power transformer and vibrator from the radio. Use the radio's original filter chokes, but replace the filter condensers (replace all condensers in the radio). You must make sure that no chassis screws are able to be touched once the set is put together, as it will now be an AC/DC set (except for the A filament supply). If you are worried about shock problems, you can purchase Radio Shack's mid-sized 12 volt transformer (I think that it's rated at about 1.2 amperes or perhaps slightly larger) for the A supply. Purchase another one for the B supply. Wire its secondary to the secondary of the A transformer, and wire its primary to the AC input of the full wave rectifier for the B supply. You may actually get away with using Radio Shack's smallest 12 volt transformers, since this radio draws a very small amount of current, but it is best to go with the larger ones just to be safe. If you have extra money to spend, try the smallest ones out first. The A supply draws very little current, and the B supply doesn't draw much, either. What originally drew a lot of current in this radio was the vibrator supply.
I can't imagine all of the above parts costing more than a total of $40. If you can fit the supplies under the chassis of the radio, remove the original radio wires from its on/off switch and splice them together as though they were connected to the switch and it was on (there are actually two switches inside of the control, which control two separate circuits....don't just splice all of the wires together. Splice the two pairs of wires together separately). Now you can connect one or both sides of the power cord of your power supply to the switch on the radio. Since the switch has two sections, you can effectively switch on and off both sides of the power cord. Now your radio will work like any other AC radio, and will be quite convenient to use. If anyone wishes to convert it back to a vibrator supply in the future, it shouldn't be hard to accomplish.
I did some rather amazing but simple things to my own farm radio that also make it sound extremely nice, more like a very nice AC set. It doesn't seem like anyone else here tries these things, though, because I never hear any commentary. If you'd like to know what they are after you've gotten your radio working, let me know.
Thomas
The filaments themselves don't draw much. The vibrator supply creates noise both acoustically and electrically. If you wish, you can go to Radio Shack and purchase their smallest 6-0-6 volt (12 volt total) transformer, a variable regulator, recommended potentiometer and resistor, a full wave bridge rectifier, some 2000 MFD electrolytics, and a circuit board, all for under $20. Wire up the supply and regulate it at 6.0 volts (or 1.5 volts if the filaments are in parallel....I forgot whether they're in series or not). If you regulate at 6 volts, build the supply using the full 12 volt winding across the AC input of the rectifier. This will allow the variable regulator to eliminate more hum. Be sure to adjust the regulator before you hook the supply up to the radio. Otherwise you may blow the tubes. The regulator and rectifier must be heat sinked properly. Once you have them in operation and feeding the radio, make sure they don't get hot. They shouldn't get warm much at all, since the filaments of the tubes in your radio draw an incredibly small amount of current.
:
:For the B supply, simply purchase one of Radio Shack's 400 volt full wave rectifiers. Connect the AC input of the rectifier to the AC cord of the filament supply. Connect the negative output of the rectifier to the radio's chassis, and the positive to where the original power transformer's center tap connected. Disconnect the original power transformer and vibrator from the radio. Use the radio's original filter chokes, but replace the filter condensers (replace all condensers in the radio). You must make sure that no chassis screws are able to be touched once the set is put together, as it will now be an AC/DC set (except for the A filament supply). If you are worried about shock problems, you can purchase Radio Shack's mid-sized 12 volt transformer (I think that it's rated at about 1.2 amperes or perhaps slightly larger) for the A supply. Purchase another one for the B supply. Wire its secondary to the secondary of the A transformer, and wire its primary to the AC input of the full wave rectifier for the B supply. You may actually get away with using Radio Shack's smallest 12 volt transformers, since this radio draws a very small amount of current, but it is best to go with the larger ones just to be safe. If you have extra money to spend, try the smallest ones out first. The A supply draws very little current, and the B supply doesn't draw much, either. What originally drew a lot of current in this radio was the vibrator supply.
:
:I can't imagine all of the above parts costing more than a total of $40. If you can fit the supplies under the chassis of the radio, remove the original radio wires from its on/off switch and splice them together as though they were connected to the switch and it was on (there are actually two switches inside of the control, which control two separate circuits....don't just splice all of the wires together. Splice the two pairs of wires together separately). Now you can connect one or both sides of the power cord of your power supply to the switch on the radio. Since the switch has two sections, you can effectively switch on and off both sides of the power cord. Now your radio will work like any other AC radio, and will be quite convenient to use. If anyone wishes to convert it back to a vibrator supply in the future, it shouldn't be hard to accomplish.
:
:I did some rather amazing but simple things to my own farm radio that also make it sound extremely nice, more like a very nice AC set. It doesn't seem like anyone else here tries these things, though, because I never hear any commentary. If you'd like to know what they are after you've gotten your radio working, let me know.
:
:Thomas