Woohoo... new chassis.

Posted: 3/31/2007 6:15:38 PM

From: Escondido, CA

Joined: 3/25/2007

Well I won this old radio on ebay. It's an old 1950s Motorola tube "portable." I want to use it for a theremin case. The chassis is steel and is covered with some leatherette stuff. I love the look and color, but I have to clean it up. If the covering looks too bad and I can't clean it to look nice, I'll probably remove it and paint the steel with a sparkle flake paint. I also want to paint over the AM frequency numbers.
The handle is actually an AM antenna. Should I just cut the connection, or should I try to use it in the circuit?
I assume also that I can use the AM coil and capacitor in the circuit.
It's great that this already has the mains connection. However, it's 2-pin with no ground (earth). Is that a problem?

The radio was said not to work, which I actually prefered. It would make me sad to take a vintage working radio and kill it.

Pic 1 (http://www.ushighway66.com/images/radio1.jpg)

Pic 2 (http://www.ushighway66.com/images/radio3.jpg)

Pic 3 (http://www.ushighway66.com/images/radio2.jpg)

Posted: 4/1/2007 5:23:35 PM

From: Florida

Joined: 11/24/2006

Wow that is an awesome radio! Maybe you should check around and see what a working model is worth. It might be worth fixing. It could be nothing more then some blown tubes. There are some sources for old radio tubes on the net...

Fred Nachbaur reworked an old AM tube radio into a theremin:
Maybe you could do the same?

As to saving the antenna handle, some of the interior parts and the ground that would probably depend on the theremin you plan to build. Are you building a kit or found a project somewhere on the internet? How good are you with electronics? Can you design or redesign a circuit to fit parts you have?

Posted: 4/2/2007 3:00:02 AM

From: Escondido, CA

Joined: 3/25/2007

I've made analog synth modules from scratch, so I can probably figure something out with this. I just ordered a Theremax kit, and I may put it in this case. Either that or I might put the kit in a clear acrylic case like the one on the Paia site (the one with the UV light and florescent paint).
Since the radio has a speaker, I may put in an audio amp. Craig Anderton's Electronic Projects for Musicians has a 1 watt audio and headphone amp circuit I could use. I could rig it up so that plugging in an external amp would turn off the internal speaker and headphone.
It would be cool to get the tube circuits working, but I have enough trouble understanding what's going on with the discrete and op amp solid state circuits. Tube circuits are a bit scary because they run such high voltages.
Since the AM antenna is just a big loop of wire, I was thinking it could be used as a theremin capacitor antenna, but it might cause more problems than it's worth. It's designed to pick up AM frequencies.
The AM tuning coil should be in there though. If I decide on a Lev antenna, it should already have a coil ready to go.

I found an ad for this radio on ebay. It's from 1956, and it does sort of remind me of a Chevy Bel Air styling. The ad shows an orange model.

Radio ad (http://www.ushighway66.com/images/radioad1.jpg)
Posted: 4/2/2007 3:46:32 AM

From: Undisclosed location without Dick Cheney

Joined: 2/21/2005

Look, a tube is basically a light bulb with some electronics in it. The most common problem with a tube circuit is that the tube dies, just like a light bulb does. So, the way a technician would diagnose a tube circuit is that they would turn the thing on and see if the tubes glow. If one of them is out, it's likely the problem, so they replace it.

In other words, they didn't actually have to touch the circuit while it's powered to see what was wrong with it.
Posted: 4/2/2007 12:00:55 PM

From: Jax, FL

Joined: 2/14/2005

That would make a nice theremin but I would definitely check it out to see what it is aorth on the colelctor market first.

With that styling and those colors it just screams 1950's, which might make it valuable to a collector.

The other component is supply. It really depends on how many were made and how many survived....
Posted: 4/3/2007 7:38:31 AM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

It's my understanding that the most common mode of failure in these old radios is failure of the capacitors. To turn the radio on without replacing these can cause damage to other components, including the power supply (transformer, etc....).
Posted: 4/3/2007 8:20:57 AM

From: Jax, FL

Joined: 2/14/2005

The old capacitors do deteriorate over time and they leak after a while.

I'm not nearly as old as the radio and I have deteriorated over time.

I occasionally leak, too, but that's a topic for a different thread....

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