Converting an old Zenith Radio?

[brokennarsil]

Hello everyone. I recently got an old Zenith tube am/fm radio and was thinking about a conversion.

The tube compliment is rather odd, it has about 8 with names like 6bj6, 12ba6, 19t8, 35c5, etc. the only ones I think I recognize are the 12at7 and 12au6.

I haven't torn it apart yet, but it doesn't seem to have any sort of proper transformer, either.

It works though! I fired it up and it plays songs like a champ. The only thing wrong with it was the am/fm knob was busted and needs to be replaced. Other than that it has a volume and one tone knob.

If I can't properly convert it, is there any way I can just wire an imput jack to it and play through? I know it's a hifi, but I can use pedals for any effects I want. And the more I think about it, I don't want to scrap it, because it's really a nice radio. If I could just play through it without tearing it to pieces that would be ideal.

Thanks everyone!

[JHow]

The tube compliment is rather odd, it has about 8 with names like 6bj6, 12ba6, 19t8, 35c5etc. the only ones I think I recognize are the 12at7 and 12au6.

6bj6 RF amp pentode
12ba6 RF amp pentode
19t8 AM/FM dectors and Af amp combined
35c5 AF output amp

You probably really are only interested in the AF tubes, but these are not very helpful guitar map tubes.

I haven't torn it apart yet, but it doesn't seem to have any sort of proper transformer, either.

Yes, this assortment of tubes suggests transformerless operation. Not really super safe, since you often find that the chassis is hooked to the mains. Sometimes its posisble to use an isolation transformer to make these circuits safer, but since much of the circuit is taken up by RF stages, you are probably better off using the chassis and sockets and coming up with your own (transformer) circuit.

If I can't properly convert it, is there any way I can just wire an imput jack to it and play through? I know it's a hifi, but I can use pedals for any effects I want. And the more I think about it, I don't want to scrap it, because it's really a nice radio. If I could just play through it without tearing it to pieces that would be ideal.

Hmm. If you don't want to gut it, and you like it as a radio, why don't you just keep it as a radio? Make a small am transmitter and broadcast your stereo into the gargae if you don't like the local stations.

[brokennarsil]

Wow JHow, you're like my own personal guru! Is there anything about this stuff you don't know?

But yeah, I'll probably just end up keeping it as is. In a perfect world (and I'm sure this isn't really feasable) I'd be able to wire it so I could flip a switch and toggle between the radio side of it and my guitar imput side. That'd be awesome. But the more I think about it the more difficult that seems.

[JHow]

I'm just fascinated with the postings where people "re-purpose" PA amps, radios, phonographs, etc. I think because the first tube device I ever worked on was a 1941 Philco "AC" AM radio. In fact I have a gutted RCA on the bench right now that I think would make something cool.

Re your idea of maintaining the radio circuits, but also amplifying your guitar, take a look at some old radio set schematics and see if you can figure out how they implemented "aux" and "phono" inputs so you could play a record player or such through the set. That was available back in the day on some sets. Maybe your set would be easy to adapt that way. On a crude level, injecting a signal into the middle lug of the volume pot will send it through the AF stage and out the speaker. There a lot of other considerations to doing this, however, like muting the rest of the radio. I admit I have not tried to do this with a guitar signal. I have the feeling that you are in uncharted waters, but maybe you're the one to do it first.

[brokennarsil]

Wow. While the uncharted waters thing sounds really neat, I have waaay too little know-how to pioneer anything in electronics

But I'll take your advice and look around some more. It's hard to believe there's nothing like this around...

It won't kill me though if I can't do anything with it. Like I said it's a great radio anyway, and makes a nifty antique fashion statement in my living room. The model number by the way is S-53555 if that means anything.

I've just been so taken by the trend of converting pa amps and other tube stuff for guitar application. This radio has been the first thing I was able to find with tubes. I've looked high and low but can't seem to find anything tube powered. It's driving me crazy!