I came into possession of a Philco 42-122 farm radio recently. The guy I got it from said it ran on 32 volts (pretty common 60 years ago in the rural community). The tubes installed don't match the schematic, or even the ID legend pasted inside the cabinet. The tubes installed are: 7B8, 7A7, 7E6, 7A4, and 43, which are substituted for a 1LA6, 1LN5, 1LH4, 1LA4 and 1LA4 respectively. It looks to me like the radio was designed to run on a 90v/1.5v battery pack, but was converted to run on 32v. The original battery cable was repaced with a standard 120v two prong plug, which no doubt plugged into the 32v system some farm house was wired for.

Question: did a 32 volt conversion just involve swapping the tubes, and replacing the original battery wires, or is there more to it than that??? I'd like to put this thing back into its original configuration.

Thanks///Jeff

I don't think that your radio was converted, it was originaly a battery set. your model is listed here on this site as a 42-123. It also have the 122 series there also, and they are all batery sets. Double chech the wiring, i think that the guy thought it was a 32 volt radio, a 32 volt radio would have had a transformer to bump up the voltage.

:I came into possession of a Philco 42-122 farm radio recently. The guy I got it from said it ran on 32 volts (pretty common 60 years ago in the rural community). The tubes installed don't match the schematic, or even the ID legend pasted inside the cabinet. The tubes installed are: 7B8, 7A7, 7E6, 7A4, and 43, which are substituted for a 1LA6, 1LN5, 1LH4, 1LA4 and 1LA4 respectively. It looks to me like the radio was designed to run on a 90v/1.5v battery pack, but was converted to run on 32v. The original battery cable was repaced with a standard 120v two prong plug, which no doubt plugged into the 32v system some farm house was wired for.
:
:Question: did a 32 volt conversion just involve swapping the tubes, and replacing the original battery wires, or is there more to it than that??? I'd like to put this thing back into its original configuration.
:
:Thanks///Jeff

Hi

Philco 42-123 is a battery operated radio. It use 1 1/2 volts for filaments and 90 volts for tube plates. This radio does not operate off of 32 volts.

http://www.nostalgiaair.org/PagesByModel/505/M0013505.pdf

Tubes starting with 7 are 6.3 volt filament types. They can be wired in series for operation off higher voltage. 43 is an older style tube for operation off of 25 volts.

Has the chassis been replaced? Does it look like the socket for the 43 was added? Both 1L and 7 series tubes use the same sockets so these could be originals.

Norm

:I don't think that your radio was converted, it was originaly a battery set. your model is listed here on this site as a 42-123. It also have the 122 series there also, and they are all batery sets. Double chech the wiring, i think that the guy thought it was a 32 volt radio, a 32 volt radio would have had a transformer to bump up the voltage.
:
:
::I came into possession of a Philco 42-122 farm radio recently. The guy I got it from said it ran on 32 volts (pretty common 60 years ago in the rural community). The tubes installed don't match the schematic, or even the ID legend pasted inside the cabinet. The tubes installed are: 7B8, 7A7, 7E6, 7A4, and 43, which are substituted for a 1LA6, 1LN5, 1LH4, 1LA4 and 1LA4 respectively. It looks to me like the radio was designed to run on a 90v/1.5v battery pack, but was converted to run on 32v. The original battery cable was repaced with a standard 120v two prong plug, which no doubt plugged into the 32v system some farm house was wired for.
::
::Question: did a 32 volt conversion just involve swapping the tubes, and replacing the original battery wires, or is there more to it than that??? I'd like to put this thing back into its original configuration.
::
::Thanks///Jeff

Also, not all 32 volt radios use a transformer to step up the voltage. Quite a few use the straight 32 volts and then have several output tubes wired in parallel (or push-pull). I don't know if much usable power could be obtained from just one #43 tube. The absence of a rectifier indicates that this set probably did operate from 32 volts, or maybe the owner tried to eliminate the need for an A battery, and operated the filaments from 32 volts, and the B supply from something else (either a battery or a 32 volt converter). It is best to go over the chassis carefully like Norm said. Various items will give you clues as to the originality of the set and its layout and such.

Thomas

This one is a curiosity. It has definitely undergone a conversion, as some of the tubes are wired in series instead of parallel. The power cord (which replaced the four-connection battery cable) is a standard 120 volt two wire two-prong plug, with one side of the plug colored red to indicate the polarity. The positive side is soldered to both terminals of one side of the double pole switch (instead of one terminal being 90 volts and the other being 1.5 volts), and the negative lead is soldered directly to the chassis (the chassis is a 42-122, type 121). I assume that when it was turned it on, 32 volts would flow thru both sets of terminals on the power switch. I couldn't follow all of the wiring on my initial look under the chassis, but it has obviously been thru a conversion.

Norm: yes, the original tube socket was removed, and one that accepts a type 43 tube was installed (with screws) in its place.

Delco made a 32 volt gas generator which was popular in rural areas where there was no commercial power back in the early decades of the last century. I wonder if there was some standard 32 volt conversion procedure for 90/1.5 volt farm radios, or if some adept radio repairmen figured out the conversion on their own? Anyone have any input on this????

BTW, "32 Volts" is hand-painted in red letters on the back of the speaker coil bracket (underlined four times no less). The tubes all test good and nothing appears to be burned underneath, so I believe all previous owners heeded the warning and didn't plug it into 120v AC.

I think I'll leave this one as is, and either look for or build a 32v power source. Do you suppose 24 1.5 volt D-cells wired in series, or four 9 volt transistor radio batteries would provide enough juice to light it up?

Jeff S.

:I think I'll leave this one as is, and either look for or build a 32v power source. Do you suppose 24 1.5 volt D-cells wired in series, or four 9 volt transistor radio batteries would provide enough juice to light it up?
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:Jeff S.

jeff,

I suspect the four 7xx tubes are wired in series (adding to 25.2V at 300ma) and the 43 to be parallel to those 4, making a string of 25V at 300ma. There should be a large resistor to drop the 32V to that 25V if my guess is correct (that would be a drop of 7V at 600ma, making it a approx. 12 ohms, 5-10W resistor).

600ma or even 300ma is way too much for standard 9v batteries. I'd suggest Alkaline D cell if you expect to run the radio only from time to time or for tetsting purpose. Now, again, if my guess is correct, you could remove the dropping resistor and feed the tubes with 24V worth of batteries instead of 32V with loss...

If you intend to run the radio on a regular basis, a 32V regulated power supply is strongly suggested. A 24VAC/2A full wave rectified, using a choke and two large caps would do nicely (as a PI filter). Or a pass Darlington transistor wired as a capacitance multiplier (the drop would be minimal and you'll be very close to the 32VDC).

Z-

If someone converted this radio from a 90 volt B battery radio to a 32 volt radio, then the radio was originally designed to operate at 90 volts. Follow the original schematic if any resistors were changed. Wire all of the tube heaters in series so that they make a total of 50 volts. Then either use a condenser or a resistor to complete the string so that it can be plugged into 120 volts AC. Purchase a small full wave rectifier from Radio Shack capable of handling about 2 amperes (not actual current, but allows for surges and such) at 400 volts. Wire it to the AC line and wire the DC output to the B circuit. Use a suitable dropping resistor between the rectifier + and the radio so that the voltages at all of the RF tubes are around 90 to 100 volts. Connect a 30 MFD condenser from the radio side of this resistor to the negative side of the rectifier. Connect the output transformer on the rectifier + side of this resistor. Also connect a 50 MFD condenser from this point to the negative side of the resistor. Connect another resistor around 50 ohms 1/2 watt between here and the rectifier.

The radio will now be an AC/DC radio so use proper precautions when handling the chassis. The chassis, if directly connected to the rectifier's negative side, will not be connected to one side of the line cord, but instead will be connected to both sides through the diodes. A shock hazard will exist no matter which way you put the plug. Be sensible when working with the radio.

You can also use a half wave diode capable of about 2 amperes at 400 volts. Wire this like you would with any AC/DC radio.

When wiring the heaters, put the 1st AF at the B- side of the line cord, and the 43 on the other side of the line cord. If you use a full wave rectifier, it does not matter which side of the line cord these two tubes are connected.

Thomas

You should check several things:

1) How are the tubes wired? Is there a dropping resisitor or ballast? It is odvious that the voltages of the tubes don't add up to 32.

2) Check the way the B+ Input was powered. Since there is no rectifier, you need to check if there is a synronus vibrator installed and a transformer, or if there was any connection for an external B battery (probably in the range between 45 and 120 volts) somewhere. It is also possible that the radio runs 32V on the plates, but this is unlikely due to the feable audio power due to the fact there is only one 43 tube for audio output with only 32V going to it.

3) 32V radios often need considerable power to run them, often between 1 and 2 amps. Keep this in mind when creating a power supply.

:This one is a curiosity. It has definitely undergone a conversion, as some of the tubes are wired in series instead of parallel. The power cord (which replaced the four-connection battery cable) is a standard 120 volt two wire two-prong plug, with one side of the plug colored red to indicate the polarity. The positive side is soldered to both terminals of one side of the double pole switch (instead of one terminal being 90 volts and the other being 1.5 volts), and the negative lead is soldered directly to the chassis (the chassis is a 42-122, type 121). I assume that when it was turned it on, 32 volts would flow thru both sets of terminals on the power switch. I couldn't follow all of the wiring on my initial look under the chassis, but it has obviously been thru a conversion.
:
:Norm: yes, the original tube socket was removed, and one that accepts a type 43 tube was installed (with screws) in its place.
:
:Delco made a 32 volt gas generator which was popular in rural areas where there was no commercial power back in the early decades of the last century. I wonder if there was some standard 32 volt conversion procedure for 90/1.5 volt farm radios, or if some adept radio repairmen figured out the conversion on their own? Anyone have any input on this????
:
:BTW, "32 Volts" is hand-painted in red letters on the back of the speaker coil bracket (underlined four times no less). The tubes all test good and nothing appears to be burned underneath, so I believe all previous owners heeded the warning and didn't plug it into 120v AC.
:
:I think I'll leave this one as is, and either look for or build a 32v power source. Do you suppose 24 1.5 volt D-cells wired in series, or four 9 volt transistor radio batteries would provide enough juice to light it up?
:
:Jeff S.

Well, it only took me about five years to get around to this one. I replaced all of the capacitors (including the two extra electrolytics whoever converted the radio to 32v installed), one tube and a couple of other parts. It works just fine. Whoever figured out the conversion from 90v to 32v for this apparently knew what they were doing.

I converted a HP 32 volt transformer that once belonged to a printer (or some other computer peripheral) to use as a power supply. That also works well.

Better late than never...

Jeff S.

I have a Midland B6B 32 volt radio. I also used the HP 31.5 power supply. It's perfect for these radios. Well regulated and about pure DC. No chopper hash emitted. Would recommend part number C7296-60024 these can be found for under $25.00

Warren,

That's the same one I am using. I found it for $8.00 on-line. I cost me about $7 for shipping, but for $15 total it was well worth it. I used a two-wire vehicle connector harness so that I could connect and disconnect the power supply to and from the radio, and also to make sure I had the polarity correct. One half of the wire harness is soldered to the radio, the other half soldered to the power supply.

Jeff

:Warren,
:
:That's the same one I am using. I found it for $8.00 on-line. I cost me about $7 for shipping, but for $15 total it was well worth it. I used a two-wire vehicle connector harness so that I could connect and disconnect the power supply to and from the radio, and also to make sure I had the polarity correct. One half of the wire harness is soldered to the radio, the other half soldered to the power supply.
:
:Jeff
:

Only five years, huh? Wish I could fox things that fast, but we are a li'l in Georgia, I guess.
Lewis

Seriously, Good work!!!