Restore an RCA R4B1 Battery Portable Radio From 1946

In this video I've repaired and restored a 1946 RCA R4B1 battery portable radio

List of tools and materials used:

Tools: needle nosed pliers, screwdrivers, slot and philips, wrenches, soldering iron,

Supplies: solder and electrical tape, plastic restorer and glue.

Parts: 3 tubes, audio transformer, oscillator coil and battery holder from donor radio, new capacitors

Test equipment: signal generator

The first step is to examine the radio for missing parts. It turned out that the audio transformer had been taken out and filament battery holder was rusty. The radio also had three missing tubes out of four. Luckily, I had a junk radio of the same type on hand that I could supply the audio transformer, battery holder and three tubes.

I examined the radio cabinet and considering it is 79 years old, it was in surprisingly good condition, with a few small cracks in the plastic and some paint scratches on the metal middle part. I just treated the plastic with Armour All and it came out with a nice sheen. I didn't repaint the metal part because it looked like honest wear. The printed tags in the back of the radio were in really good condition and add to the authenticity and history of the radio.

Almost all of the wires in the radio have cracked and rotten insulation, so I will need to replace them with all of the capacitors.

As I opened up various parts of the radio, I replaced wires with ones of the same or similar colors.

Not knowing if the speaker was any good, I checked it with a 1000 Hz test tone and it turned out to be good.

I soldered in the missing audio transformer and wired it to the speaker and output tube socket. I tested it with an audio test tone and the speaker sounded good.

After Installing tubes, replacing old capacitors, old wiring and added the new A battery holder, I attached the radio to power and put an oscilloscope on the IF oscillator/converter tube. I should've seen a sign wave but saw nothing but noise.

I started doing continuity checks with a VTVM and found that the oscillator coil had a broken connection. I was getting a loud hum when I put my fingers on the first tube and also on the last tube. When I touched a screwdriver to the control grid of the last tube, I got a loud hum. This showed that the tubes were amplifying and passing signals through the chain. I figured that I should replace the oscillator coil with the one from the junk radio.

I swapped the oscillator coil from the donor radio to this radio. I reapplied power to the radio and attached the scope to the converter tube, I saw the sign wave that is supposed to be there and as I moved the tuner the frequency changed. I removed it and heard music from the radio. I did an alignment on the IF transformers because the oscillator coil had slightly different characteristics than the one that was in previously. I checked out the performance and it was excellent. I made up a battery pack of 6 nine volt batteries adding up to 54 volts in series and installed the standard 1.5 volt flashlight battery for the filaments.