Vintage radio: actually being a radio
Sep. 30th, 2025 08:22 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
arisoturaI finally received the appropriate vacuum tubes for the vintage radio!
I was so excited that I went to the hackerspace the same day, to try them out. I went with a friend who was also quite interested in the radio.
Once I was there, I quickly swapped in my new tubes. I also checked the coil that is connected to the resistor that was burnt, I was concerned that it might have been damaged, but it measured fine.
(EDIT- I realized I've never brought up that resistor, so, here it is)
This is R10 on the schematic. I noticed it while replacing the capacitors. I don't know how I missed it before, because it wasn't caused by my testing, it was already burnt when I got the radio.
R10 should be 2.2 kiloohm, but this one measured in the megaohm range. I of course replaced it, but I was concerned that whatever caused it to fail could have damaged surrounding components, especially L24.
(EDIT end)
Then I turned on the radio. This time, the receiver came to life! It was a bunch of noise at first, but eventually, we received actual radio signals.
We figured out a bit more about how this radio works.
The visual indicator tube isn't very visible, because it isn't aligned properly. However, it works quite well. It indicates whether the radio is picking up a signal, and how strong that signal is. Nifty!
The Selektiv/Lokal switch seems to change the tuning mode, depending on whether you're looking for a radio station or whether you're already tuned in, it seems to change how sensitive the receiver is. I'm not exactly sure how to describe it, but that's the idea...
The AM bands use the "ferroceptor" antenna. There isn't much on those bands, but I was able to receive a foreign station... not bad, considering the hackerspace is in a basement.
The FM band uses the external antenna. We were able to receive several FM stations quite well.
-
There is still room for improvement with the radio.
For example, fixing that missing button.
There's also a little issue with FM tuning. Pressing the UKW switch moves a mechanism that lets the tuning knob control the FM tuner instead of the AM tuner, but it's not completely disengaging from the AM mechanism, so it kind of tries to control both. I need to figure out a way to fix this.
The FM needle is also not very visible. I should figure out if I can improve it...
I also damaged some of the art on the front panel when I cleaned it, back in July. It's minor, but I feel bad about it...
And last but not least, we need to figure out a way to mount the indicator tube properly, so it's aligned to the window in the front panel.
-
All in all, this is pretty cool. This radio is 67 years old, it was a wreck... and it's working pretty well. Just with new capacitors, and the adequate tubes. That's great!
I'm also not a professional. I have some knowledge of electronics, but this is my first time working with something like this - point-to-point wiring, vacuum tubes, ...
This leaves me wondering what happened to the tubes. It's like someone stole the EF89 tubes from this radio, and someone else tried to replace them. Maybe the ECH81 was moved to the wrong socket, which would explain why there was two of them... weird.
The GT12AY7 was recent, so it's like someone else tried to revive this radio at some point. Probably the same person who added the 3.5mm cable for audio input.
I should have paid more attention to those tubes. Since the other tubes were correct, I trusted them, but I can imagine how such a situation (having completely incompatible tubes in) could cause problems.
I will likely post more about this radio, but this is pretty good for now!
I was so excited that I went to the hackerspace the same day, to try them out. I went with a friend who was also quite interested in the radio.
Once I was there, I quickly swapped in my new tubes. I also checked the coil that is connected to the resistor that was burnt, I was concerned that it might have been damaged, but it measured fine.
(EDIT- I realized I've never brought up that resistor, so, here it is)
This is R10 on the schematic. I noticed it while replacing the capacitors. I don't know how I missed it before, because it wasn't caused by my testing, it was already burnt when I got the radio.
R10 should be 2.2 kiloohm, but this one measured in the megaohm range. I of course replaced it, but I was concerned that whatever caused it to fail could have damaged surrounding components, especially L24.
(EDIT end)
Then I turned on the radio. This time, the receiver came to life! It was a bunch of noise at first, but eventually, we received actual radio signals.
We figured out a bit more about how this radio works.
The visual indicator tube isn't very visible, because it isn't aligned properly. However, it works quite well. It indicates whether the radio is picking up a signal, and how strong that signal is. Nifty!
The Selektiv/Lokal switch seems to change the tuning mode, depending on whether you're looking for a radio station or whether you're already tuned in, it seems to change how sensitive the receiver is. I'm not exactly sure how to describe it, but that's the idea...
The AM bands use the "ferroceptor" antenna. There isn't much on those bands, but I was able to receive a foreign station... not bad, considering the hackerspace is in a basement.
The FM band uses the external antenna. We were able to receive several FM stations quite well.
-
There is still room for improvement with the radio.
For example, fixing that missing button.
There's also a little issue with FM tuning. Pressing the UKW switch moves a mechanism that lets the tuning knob control the FM tuner instead of the AM tuner, but it's not completely disengaging from the AM mechanism, so it kind of tries to control both. I need to figure out a way to fix this.
The FM needle is also not very visible. I should figure out if I can improve it...
I also damaged some of the art on the front panel when I cleaned it, back in July. It's minor, but I feel bad about it...
And last but not least, we need to figure out a way to mount the indicator tube properly, so it's aligned to the window in the front panel.
-
All in all, this is pretty cool. This radio is 67 years old, it was a wreck... and it's working pretty well. Just with new capacitors, and the adequate tubes. That's great!
I'm also not a professional. I have some knowledge of electronics, but this is my first time working with something like this - point-to-point wiring, vacuum tubes, ...
This leaves me wondering what happened to the tubes. It's like someone stole the EF89 tubes from this radio, and someone else tried to replace them. Maybe the ECH81 was moved to the wrong socket, which would explain why there was two of them... weird.
The GT12AY7 was recent, so it's like someone else tried to revive this radio at some point. Probably the same person who added the 3.5mm cable for audio input.
I should have paid more attention to those tubes. Since the other tubes were correct, I trusted them, but I can imagine how such a situation (having completely incompatible tubes in) could cause problems.
I will likely post more about this radio, but this is pretty good for now!
