AM Tube Radio Restored And Given MP3 Playback Too


This AM radio looks a bit like it did coming out of the factory. But there are a lot of changes under the hood and that faceplate is a completely new addition. The project really is a restoration with some augmentation and [Michael Ross] did a great job of documenting the project.

The Kenyon radio was built in 1946 and uses vacuum tubes for the amplifier. Considering its age this was in relatively good shape and the first thing that [Michael] set out to do was to get the electronics working again. It involved replacing the messy collection of capacitors inside. He then cleaned up the tubes, checking for any problems, and put the electronics back together to find they work great!

He cleaned up the chassis and gave it a new coat of finish. The original dial plate was missing so he built a wood frame to match a dial scale he ordered. The bell-shaped brass cover hides the light that illuminates the dial.

He could have stopped there but how much do people really listen to AM radio these days? To make sure he would actually use the thing he added an Arduino with an MP3 shield. It patches into the antenna port via a relay, injecting modern tunes into the old amplifier circuit. Catch a glimpse of the final project in the video after the break.

46 thoughts on “AM Tube Radio Restored And Given MP3 Playback Too

  1. WOW! This is a tour de force, Woodwork, brass hammering, metal lathe work, tubes AND an aurdino, amazing! I have just one question, what the hell is that commercial for “Johnson Wax”, is that some kind of sex lube?

  2. Fantastic. Thank you so much for not destroying the thing. I’ve done this before (although never to this level of finish detail!) and I can say that not only is this a very useful project, but it will sound really, really good.

  3. Really nice work, well done. Just one suggestion: add a reverse biased diode, like an 1N4001, across the relay coil to soak up the back EMF generated when the coil is de-energized. Your 2N2222 will live longer and thank you for it.

      1. stoopit browser. As an old-radio fnatic/restorer, I recommend taking all such protective steps. This is a great example of one which wouldn’t be immediately thought of, but which will make for a much happier life for the project. Also, please forgive any typois… as I type this, I can’t see any letters, onlty a cursor moving in an empty box. Not sure if it’ smy browser or something on the HAD siad, but it’s danged annoying.

          1. That reminds me of a review I saw on newegg for a keyboard. It went something like “Iboughtthiskeyboardtwoweeksagoanditworkedgreatatfirstbutthenasinglekeystoppedworking.Guesswhich.”

  4. Awesome job, craftsmanship, and respect for the aesthetics and preservation of vintage gear. This project was a pleasure to look at. A++

    A couple of warnings of a general nature:

    I didn’t see a power transformer on this radio chassis. If not, that means that the chassis has a very good chance of being (electrically) hot with respect to earth ground. I noted reference to a polarized plug, but even so, you are still then at the mercy of whoever wired your wall outlets. If the chassis should become hot, anything that represents a potential path from chassis to real ground could result in severe damage or injury. (There is a story about a prison inmate, some ears ago, who wired a set of headphones to a hot-chassis television in his cell. He electrocuted himself when he sat down on his stainless-steel toilet to relieve himself.) A very easy way to fix this problem is to use an isolation transformer. They’re not that expensive and I wouldn’t run any vintage hot-chassis set without one.

    The other warning to potential radio restorers of non-transformer sets is this: Excercise caution when replacing a “bad” power cord. Some old radios used power cords that contained resistance wire. If you replace that kind of cord with a copper power cord, chassis voltages may be way too high. You could end up popping tubes or frying other components.

    Finally, as to the comment “… how much do people really listen to AM radio these days?” I do– a lot. I enjoy news, sports, and talk radio. Ironically I feel the same about FM as some do about AM. How can someone listen to FM stations and hear the same 10 songs in rotation for months at a time?

    1. This is actually the only true tube radio rebuild in the last few weeks. In the even Mike didn’t post this, and we found out about it, he should been punished with a thousand lashes of Ann Landers wet noodle every day for the rest of his life. ;)

  5. Great project, looks awesome! Kudos for keeping the original electronics! I’m having problems getting onto the linked site so could anyone here clarify why this has/needs an arduino?

    1. The arduino component where used to create 7 pseudo radio stations program with recorded material from the 40’s& 50’s that can be “tuned in” by” by used the radio’s standard tuning. A clever addition to a nicely restored radio that doesn’t negatively change the basic radio much at all & the slight modification to gets the mp3 content into the radio can reversed easily.

  6. probably gonna catch hell for this but, did it really need an arduino? or any added electronics for that matter? a simple headphone stereo out to am transmitter is so drop dead simple to build and not to mention you just tune the radio into your transmitters broadcast freq. and tada! no danger of frying an arduino or ancient stereo with cross emf. all in all i loved the project but i cant help but question if there was an arduino because: arduino!

      1. @Mike, i don’t know him or her but I think your boss might catch on to the idea it is just a music player in a radio disguise.

        An idea for you might be a music player plus transmitter in your car. Then just bring a plain radio into work. I don’t know how far your desk is from the parking lot or what kind of walls are between. That might require more power than is legal unlicensed. Be careful with that.

        Also, chose your playlists well since you will only be able to adjust them on breaks.

        1. If he’s close enough to get a legal radio transmission through, he can also get a remote to work. There’s no policy against remotes, now is there? It’s also easier to queue fake advertisements that way if someone starts to wonder at the ad-lessness.

    1. No!

      If you read the article that isn’t the same thing. Rather than a single AM transmitter on a single channel his Arduino reads the position of the tuning capacitor and choses different content based on that. In other words, it simulates a band full of old-time radio stations as though the radio had some sort of connection to the past. That’s a pretty neat effect that would require shelves full of AM transmitters to duplicate the other way.

    2. You’re right that a transmitter would easily get music into the radio, but this project takes that idea a step further by simulating multiple vintage radio stations.

      The Arduino has a potentiometer attached, which is connected to the tuning string by a pulley. When it detects the tuner is in the right spot, it switches the amplifier circuit over to the MP3 shield and plays appropriate music. It looks like they set it up with several faux-stations that play different kinds of content.

    3. Evidently you did read the builder’s log, or you have an extreme prejudice against the arduino. No an arduino wasn’t used because it’s an arduino, although builder select it because he was familiar with it. The arduino, and associated shield was used because it was a simpler way to create 7 separate pseudo radio stations dispersed through the band, one would tune in as they would tune in a broadcast station. Because this is RF first & foremost I’m going to use the term hamgineering, this clever use of and arduino and implementing it, this is home shop hamgineering at it’s best. IMO opinion you are overstating the hazards to both the restored radio & the solid state add on equipment.

  7. Nicely done! If only I had seen this around Christmas when my sister charged me with a similar project. She got an old AM/Shortband radio from our uncle and wanted me to swap in a digital 1 Watt amplifier. I ultimately decided to build a “three” tube amp with the exception that the rectifier tube was replaced with a solid state full bridge. I would have loved to retain the original AM/Shortband circuitry, but couldn’t find a guide on how to patch in a signal from a MP3 player. Kudos to this guy for going the full mile!

  8. Seven transmitters wouldn’t be hard to do. He streams one of 7 at a time depending on dial position. Cute radio, but it’s post war hot chassis. It’s meant to be sealed up period. Even that light bulb is hot.
    I wouldn’t bet my gear and life on a 5mm piece of wire soldered on to the edge of an old plug. Two wire unpol or 3 wire w/ gnd. I hate those bastard one way 2 prong.
    It hurts more to hear the big band era pissed on by MP3’s stain, 5K bandwidth slopped further with the watery sound. Other than there is probably no safe source of oldies radio etc on the web, so blind and deaf we have become with pissing on every source file of sound ever created. Provenance of sound.

    1. Chill, man, all de kiddies be deaf now from de MP3 playuhs man, and hear little of de high fre-quen-cies and wouldn’t know HiFi if it bit ’em in de bum…

  9. A great A+ project! I have a couple old radios, and you have inspired me to build one myself! A couple comments, though:

    1. Your documentation says you opened the “antenna” lead to insert your MP3 sound. This should say “audio”, not “antenna”.

    2. The radio will work better if you put the Arduino in a metal box. I’ll bet that many of the whistles and birdies in the sound are coming from the Arduino.

    3. Hot chassis radios are reasonably safe with the polarized plug, but only when assembled so there is *NO* exposed metal that is connected to any part of the radio’s wiring. The Radio Shack audio transformer does *NOT* have adequate insulation to handle AC isolation, so I would treat all of your Arduino wiring as if it too were connected to the AC line. It’s tough to make it safe this way, so the best solution is to add an isolation transformer as another commenter suggested.

  10. As well as the hot chassis cautions mentioned above, the other thing to mention is that some SMPS phone chargers can generate an awful amount of RF hash that might be picked up by the existing radio circuitry. I’d be curious to know it the received static is increased and reception sensitivity decreased when the phone charger SMPS is on. Ferrites could be added to some of the cabling going into and out of the SMPS to reduce the amount of RF leaking out if this is indeed the case.

  11. Awesome.. I’m doing something similar right now. In the “getting the bastard going” phase. I have some serious problems in the radio section of my radio though, still working through repairing/restoring. Mine does SW/MW/LW and has a phono input. My amp part of the circuit is fine. Was looking to use a Raspi to stream internet radio, but have figured a cheap android phone will be … er… cheaper. Love the idea of “tuning” – might have to borrow that idea.

  12. If you did want to add an isolation transformer, they can be a little harder to find, more expensive than step-down transformers. Another option is to get two step-down transformers of the same voltage and connect their secondaries together. It’s a bit inefficient but the radio was probably designed for 105 or 110 volts and your modern outlet probably puts out 120 or more so this could even be a good thing.

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