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The original AM radio in my 56 quit working except for a steady hum that is unaffected by the volume control. I double checked all connections and ohmed out the antenna lead and all is well. Any ideas on what may have went "belly up" or other things to look for/try? Thanks
 

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There's a member here Dr Delco who rebuilds them and has parts ,,PM him maybe he can help you ,,,:anim_25:
 

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The original AM radio in my 56 quit working except for a steady hum that is unaffected by the volume control. I double checked all connections and ohmed out the antenna lead and all is well. Any ideas on what may have went "belly up" or other things to look for/try? Thanks
Change the vibrator tube to a solid state one. It quiets the hummm. Try a new OZ4 tube also.
 

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Is it a mechanical vibration sound or a hum from the speaker?
 

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Take the tubes down to Seven-Eleven and test them.









Oh, wait, they don't have tube testers at 7-11 anymore. :)
 

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the same thing happened to my 55's radio. I changed the 0Z4, the vibrator, still nothing. Then I hit the internet up for some answers. After 60 years the paper capacitors dry up and your radio just stops functioning. I found the wiring schematic and ordered all the modern poly capacitors to replace the old ones, soldered them in and my radio works again. This probably wasn't what you wanted to read (not a quick fix) but it's probably the culprit. Total cost might be $50 as I also replaced all the tubes and vibrator (not the problem). Let us know.
 

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the same thing happened to my 55's radio. I changed the 0Z4, the vibrator, still nothing. Then I hit the internet up for some answers. After 60 years the paper capacitors dry up and your radio just stops functioning. I found the wiring schematic and ordered all the modern poly capacitors to replace the old ones, soldered them in and my radio works again. This probably wasn't what you wanted to read (not a quick fix) but it's probably the culprit. Total cost might be $50 as I also replaced all the tubes and vibrator (not the problem). Let us know.
Would you have a parts list of what you changed & ref to wiring diagram :)
 

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On my desktop computer I have all my research and links, I'm currently on a mobile device. Quick links would be:
check here for a diagram for either deluxe or standard radio:
http://chevy.oldcarmanualproject.com/radios/index.htm

go here for the caps:
http://justradios.com/
this guy is in Canada but his order form is easy to digest and you can get all the caps you need in one place instead of thumbing through a 4 inch Mouser or Digikey catalog. Also since your tubes create HUGE voltage you will need a couple of big volt/low microfarand caps which Justradios has.

go here to read up on the process of recapping:
http://www.antiqueradio.org/recap.htm

Read the section about electrolytic capacitors a couple of times. That was the hardest part of the recap because you have to use 3 caps to replace one multi-cap can.
It helps to have a fancy variable heat soldering iron for low heat delicate work and high heat chassis solders.

Like any project vintage or otherwise do a lot of research and print a lot of schematics. It's not a cake walk but if you can follow a 60 year old diagram and can solder you can do it. Safety is paramount!!! These old tube radios can store energy even after they are turned off and they create Huge voltage so use one hand only while working in there.
 

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On my desktop computer I have all my research and links, I'm currently on a mobile device. Quick links would be:
check here for a diagram for either deluxe or standard radio:
http://chevy.oldcarmanualproject.com/radios/index.htm

go here for the caps:
http://justradios.com/
this guy is in Canada but his order form is easy to digest and you can get all the caps you need in one place instead of thumbing through a 4 inch Mouser or Digikey catalog. Also since your tubes create HUGE voltage you will need a couple of big volt/low microfarand caps which Justradios has.

go here to read up on the process of recapping:
http://www.antiqueradio.org/recap.htm

Read the section about electrolytic capacitors a couple of times. That was the hardest part of the recap because you have to use 3 caps to replace one multi-cap can.
It helps to have a fancy variable heat soldering iron for low heat delicate work and high heat chassis solders.

Like any project vintage or otherwise do a lot of research and print a lot of schematics. It's not a cake walk but if you can follow a 60 year old diagram and can solder you can do it. Safety is paramount!!! These old tube radios can store energy even after they are turned off and they create Huge voltage so use one hand only while working in there.
Thanks for the quick reply, I have the equipment at work including various size caps, if I have a break down of what I need I`ll look here first :tu
 

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keep us posted. Remember only replace the paper or waxed caps, not the ceramic and mica caps which are rated in picofarands. The previous link covers all this.

Question: Which radio do you have, standard (no push buttons) or Deluxe (with push buttons).
 

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Take the tubes down to Seven-Eleven and test them.

Oh, wait, they don't have tube testers at 7-11 anymore. :)
I remember doing that for tv and stereo tubes. It sure was simpiler then, but the only thing I have left is tubes for is my old stereo components. Showing my age a little. :)
 

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keep us posted. Remember only replace the paper or waxed caps, not the ceramic and mica caps which are rated in picofarands. The previous link covers all this.

Question: Which radio do you have, standard (no push buttons) or Deluxe (with push buttons).
Technically, ALL capacitors can leak, even the pF ones. But, a constant hum is usually caused by the big-honking 20 mfd electrolytic capacitors in the power supply.

The big thing to note is the capacitance and voltage rating. Never reduce the rated voltage. In the power supply, the capacitance isn't super critical. The parts list calls for 20 mfd in 25 and 400 volts. But, if all you've got handy is 22 mfd capacitors, they'll be fine.

ALWAYS observe the polarity on electrolytic capacitors. If you put them in backwards, they'll explode.
 

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Technically, ALL capacitors can leak, even the pF ones. But, a constant hum is usually caused by the big-honking 20 mfd electrolytic capacitors in the power supply.

The big thing to note is the capacitance and voltage rating. Never reduce the rated voltage. In the power supply, the capacitance isn't super critical. The parts list calls for 20 mfd in 25 and 400 volts. But, if all you've got handy is 22 mfd capacitors, they'll be fine.

ALWAYS observe the polarity on electrolytic capacitors. If you put them in backwards, they'll explode.
X2 to what he said with this addition: I only mention the picofarands to denote which caps to leave alone for ease of identification. The mica caps can throw off your tuning if you replace them. Also make sure to clean any flux off of your joints or you could create a short, I learned from experience!
 

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I'll ditto the vibrator tube......:anim_25:
:gba:
bowtie-trifive
The key is whether the hum is coming out of the speaker or not. Vibrators don't hum through the speaker. Bad capacitors do.

BTW and FWIW - there are "filter" capacitors, "tuning" capacitors, and "coupling/bypass" capacitors. Replacing the tuning capacitors does require "realigning" the radio with the proper test equipment. The others can be replaced without messing anything up.
 

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Discussion Starter · #18 ·
Here is the upadate. My radio is manual tune and the hum was through the speaker. Took it to a radio repairman near Indianapolis and he replaced the vibrator, oz4, and the paper and wax caps, and a can that supposedly holds capacitors (I could be wrong on that one); but anyway, works great!
 
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