GTfastbacker Posted March 13 Report Posted March 13 (edited) Gentlemen, The original tube radio in our Dodge 41 still works. With an AM transmitter you can listen to Sinatra and Louis Armstrong very well. Unfortunately, the device hums immediately after switching on and it becomes very audible when the tubes are warm. As a comparison, it sounds like a transformer humming. What could this be and how can you fix it? Does a tube have a short in the heating? Thank you Joe Edited March 13 by GTfastbacker Quote
Plymouthy Adams Posted March 13 Report Posted March 13 this is what happens when a old radio don't know the words to the new songs..... 3 Quote
Sniper Posted March 13 Report Posted March 13 44 minutes ago, GTfastbacker said: Does a tube have a short in the heating? Nope, it it did it wouldn't work. probably the filter capacitors are bad. 1 Quote
Ivan_B Posted March 14 Report Posted March 14 +1: most likely its the filter capacitors, if it hums right away and the volume adjustment does nothing - this is it. If it is still original, you'll need to re-cap it, anyway, so start with that: Quote
GTfastbacker Posted March 14 Author Report Posted March 14 (edited) anyone please can provide a wiring schematics for that specific 41 Dodge Radio? The Tag has gone, I have no idea about the Brand or Model Number of these Radio. The only thing I know for sure it is the original radio belongs to our D19 Thank you Joe Edited March 14 by GTfastbacker Quote
SteveR Posted March 14 Report Posted March 14 (edited) 11 hours ago, GTfastbacker said: Unfortunately, the device hums I have always hated it when you hear someone singing beautifully and then someone ruins it by humming off-key. I wish I had a answer but that was the best I could do. My 37 was fitted with a radio but it seems to be somewhere between here (England) and Montana where the car came from. Edited March 14 by SteveR 1 Quote
hi_volt Posted March 14 Report Posted March 14 Is it humming coming through the speakers or is it the hum of the mechanical vibrator inside the radio chassis? If it comes on immediately after you switch it on, it could be the vibrator you're hearing. The old car radios use a mechanical vibrator to convert the low voltage DC input to AC so that it can be stepped up and rectified to a couple of hundred volts to bias the plates of the tubes. The vibrator will start humming immediately when the radio is turned on and you'll be able to hear it coming from inside the radio itself. If the hum you're hearing is coming out of the speaker, it's likely the filter capacitors are bad (leaky) and will need to be replaced. 1 Quote
Ivan_B Posted March 14 Report Posted March 14 3 hours ago, GTfastbacker said: anyone please can provide a wiring schematics for that specific 41 Dodge Radio? Did you already look in the thread I posted, or inside your own radio? Quote
p15-1948 Posted March 14 Report Posted March 14 They make electronic vibrators to replace the old mechanical units. The McPherson College has a automotive restoration program and they rebuilt my 49 and used the electronic vibrator in it. joe@classicautoelectric.com 1 Quote
Sniper Posted March 14 Report Posted March 14 Wow, I used to deal with tubes in the Navy, but we didn't use mechanical vibrators, no need we had AC. So that issue never crossed my mind. Quote
GTfastbacker Posted March 14 Author Report Posted March 14 3 hours ago, Ivan_B said: Did you already look in the thread I posted, or inside your own radio? Oh, im so sorry. I didn't saw its a link..... 😅 Will read it tonight. THANK YOU !!!!! Quote
GTfastbacker Posted March 14 Author Report Posted March 14 3 hours ago, hi_volt said: Is it humming coming through the speakers or is it the hum of the mechanical vibrator inside the radio chassis? If it comes on immediately after you switch it on, it could be the vibrator you're hearing. The old car radios use a mechanical vibrator to convert the low voltage DC input to AC so that it can be stepped up and rectified to a couple of hundred volts to bias the plates of the tubes. The vibrator will start humming immediately when the radio is turned on and you'll be able to hear it coming from inside the radio itself. If the hum you're hearing is coming out of the speaker, it's likely the filter capacitors are bad (leaky) and will need to be replaced. It starts immediately after switching on. So I think I hear this vibrator inside the radio working. Also the hum comes out of the Speaker so maybe the Capacitors are toast too. Will look for the replacement parts and start rebuilding it. Thank you! Quote
Ivan_B Posted March 14 Report Posted March 14 (edited) The mechanical vibrator does make a noise while operating, but it is way different from the condenser hum. If you disconnect the speaker and turn-on the radio, you will hear the vibrator buzz. It is normal, and usually not audible while the radio speaker is working over it. In fact, when the radio is cold, the speaker does not "kick-in" until a couple seconds later. So when you turn it on, you hear the vibrator first, and then the speaker a bit later. If the speaker also hums and volume control has no affect, if the filter condenser. Although, if you are still able to tune the stations, it might not be the filter condenser. When it is bad, you get no stations just the hum at constant volume. If the radio has not been re-caped before, you'll need to replace all the condensers anyway. This will likely take care of the issue (if any). When you replace your original 3-in-1 filter condenser with the 3 electrolytic ones, make sure that you follow the proper polarity as indicated on the new caps (+ is actual +, - is actual -, and not your positive ground). If you don't, you'll have to buy new caps like I did 😇 Also, here is some more useful troubleshooting info: Edited March 14 by Ivan_B 1 Quote
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