Philco Tube Radio
Nov 6, 2013
A couple of months ago, a woman came by with a beautiful old antique cathedral-style table radio. The cabinet was perfect – she had just had it restored – but the radio did not work at all. I agreed to rebuild it for her.
It took a lot of effort, spread over a long period of time ?- otherwise it would have been cost prohibitive – and I ended up replacing almost every part in it. And then, just when I finally got it working, after a few minutes of flawless operation, the rectifier tube went out! Fortunately that is the one and only tube in this 80 year old set that can be replaced with a modern semiconductor.
See the missing tube? Underneath, on the left, you can see the two little tiny diodes I replaced it with. How things have changed in 80 years!
You can also see all the other new parts I had to put in, and a lot of old frayed wires that had to be replaced.
I also had to replace the speaker, which was made of paper and thus was crumbling like a damp soda cracker. If you know anything about these old sets, you know that the speaker had a “field coil” which is part of the power supply, and a “speaker transformer” to connect the sound from the plate of the audio tube. Once I had replaced the big, worthless original power supply capacitors with much smaller modern caps, there was plenty of room to put the speaker transformer on the main chassis.
But what about the field coil? That part was integral to the speaker.?Solution: I replaced it with a 120 ohm resistor and a pair 0.1H chokes. Worked great!?Here’s a closeup of the “field coil” rig-up, with the resistor heat-sunk to the chassis and the chokes hot-glued to the resistor:
To replace the speaker, I had to grind out eight rivets with a Dremel tool, then I epoxied a modern speaker into the original speaker frame so it will fit properly into the original cabinet. That part alone took more than an hour.
I’m looking forward to dropping it back into the gorgeous restored cabinet and seeing the look on the owner’s face when it plays. I asked her about replacing the dial, I thought with everything else in tip-top shape it would be a shame not to. But she deferred. Maybe she’ll change her mind. I took the light bulb out to take the photos.
