Anyone here into vintage AM tube radios? No radio signal after recap.

stevehollx

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Posted over at antiqueradios.com but not getting much traction. Restoring a 1934 RCA victor Model 211 AM/shortwave console radio.

Built some guitar amps (5e3, SLO, plexi…) before.

Looked stock. Wife refinished the cab.

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It could barely pick up a station when I got it, and the 6b7 tube lead was shorting, and there was a bunch of signal wire dry rot. So replaced that stuff and all the paper/electro caps.

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Now on power up I get a amped signal, but its just kind of a pulsating noise. Not picking up a signal. Tube socket voltages seem relatively in the neighborhood, given specs from this era were like +/- 20% and our line voltage is hotter.

Any guidance on how to troubleshoot these types of problems? I have no clue how the oscillator side of this stuff works.

I’m maybe even considering my issue my be on the physical plane—do I need an external antenna hooked up? Like an AM loop (tunable, or non tunable)?

More details over at the antiqueradios post, if that’s permissible to cross link:
 

stevehollx

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Also thinking about how to get some help locally—is this the type of stuff going to the local HAM club would be into? Are they welcoming to someone that doesn’t have a call sign license but likes to tinker in old tech?
 

Jon Snell

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The first thing I would do it check that no small value capacitors have been change because that can knock the IF strip completely out and run at the wrong frequency. Using your oscilloscope, check the oscillators are running properly and alighn the IF strip using the service manuals instructions.
Always check the capacitors before replacing them as they can be perfectly OK and cause greif, much like you are having now.
I think you will get more response from Antique Radio than here.
Check the photos of the radio before you undertook any work, to ensure everything is in the correct place and correctly connected. It is very easy to cross a wire/component or even select the wrong multiflier for a capacitor.

It may be worth contacting Glasslinger for advice, https://www.youtube.com/results?search_query=glasslinger+website bit of an odd guy but very very knowledgeable.
 

Milspec

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I have a few restored Zenith Trans-Oceanics that drove me crazy rebuilding. No expert, but a few things to consider:

1. Replacing caps is a surgeon's touch task with all those brittle leads and wires. You end up moving things around just to get at them and it is very easy to have caused a break along the way. Check everything around the caps that you replaced.

2. You often need to re-align the set after a cap job. Make sure the tuner string / wire is still in tact and tight. Refer to a manual on re-alignment as it is different for each set.

3. The antenna should be built in and many use a rather unique method of grounding. I have seen some that ground to the carrying handle, so trace the antenna all the way and look for breaks.

How much background noise is there? If a lot, you need to dig into the power section. The good news is that they didn't use much power so the tubes often last a lifetime....it is just everything else that doesn't.

Looks like a beautiful radio from here, well worth rebuilding.
 

stevehollx

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Thanks everyone. Sooo I sprayed contact cleaner on the volume pot, and then hooked up a about 15’ of wire to the antenna terminal (no antenna built in the cab), took it outside, and got a few radio channels! Sometimes the easiest solutions are the right ones…



Ordered new lamps for the display panel since they are blown, and also ordered a tunable loop antenna. I still can’t find a good source as to what the ‘authentic’ antenna for this era in the 1930s would be. Just random 100’ out a window or something maybe?

Not sure if I will wire a small loop and use the tunable loop as a coupling loop, or if I will hard wire the tunable loop straight in.

Only thing left now is to repair the dry rotted speaker.

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May take this to a speaker repair pro as the surround is beat in several spots and the cone has a 4” and 2” crack in it, and a crease from the crack. Last time I tried to get a speaker repaired it was a really bad experience so not quite sure the best path on that part yet…
 

Milspec

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AM doesn't require an external antenna and the SW normally included a coil antenna of some type. The Zenith portables that I have use a telescoping antenna for SW and a coil antenna that you can suction cup to a window for use on a train or something.

A floor console that is just AM/SW should just have an internal antenna consisting of a coil of copper wire.

Glad to hear you found some success, but I admit to being a little confused by the solution. Sadly, there isn't a lot of chatter on the SW channels these days. I can reach Canada and Mexico on a good night, but only about 1-2 stations worth.
 

dogmeat

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......ahhhhhhhhhh sorry MilSpec... I really respect your posts but I gotta disagree. I recently redid an AM car radio (Studebaker) that would not pick up anything without an external antenna. I farted with this thing on the bench (after a thorough service) for a couple says tracing and tracking with poor results & then on a whim stuck a piece of welding rod in the antenna and bang... zoom.. got it all
 

stevehollx

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Yeah agreed. The manual references an external antenna and the hookup is clearly there labeled for it. The lead from it is just a straight 6” lead under the chassis to the vari cap.

And the can certainly has no wire and doesn’t seem to have a trace of wire ever being mounted in it. It is an open back cab.
 




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