Hi - I could use a little holiday help!! - I just restored a 1933 United Motors 980455. Complete resto with all new caps, wire, and electronic vibrator. Radio works excellent - except - with the volume turned all the way down I can hear a high pitched type buzz. Not one of those real loud buzzes just a constant higher pitched buss coming out of the speaker. At higher volumes you cannot notice it as it is drowned out by the sound of the station. I can reduce the buzz some with a cap from the 41 tube pin 6 to ground but I think that is just clipping the higher frequencies and makes the sound from the speaker a bit low and muffled. Any help or thoughts are greatly appreciated.

:Hi - I could use a little holiday help!! - I just restored a 1933 United Motors 980455. Complete resto with all new caps, wire, and electronic vibrator. Radio works excellent - except - with the volume turned all the way down I can hear a high pitched type buzz. Not one of those real loud buzzes just a constant higher pitched buss coming out of the speaker. At higher volumes you cannot notice it as it is drowned out by the sound of the station. I can reduce the buzz some with a cap from the 41 tube pin 6 to ground but I think that is just clipping the higher frequencies and makes the sound from the speaker a bit low and muffled. Any help or thoughts are greatly appreciated.

::Hi - I could use a little holiday help!! - I just restored a 1933 United Motors 980455. Complete resto with all new caps, wire, and electronic vibrator. Radio works excellent - except - with the volume turned all the way down I can hear a high pitched type buzz. Not one of those real loud buzzes just a constant higher pitched buss coming out of the speaker. At higher volumes you cannot notice it as it is drowned out by the sound of the station. I can reduce the buzz some with a cap from the 41 tube pin 6 to ground but I think that is just clipping the higher frequencies and makes the sound from the speaker a bit low and muffled. Any help or thoughts are greatly appreciated.

High pitched buzz, huh? Just off hand I wonder what frequency that electronic vibrator operates? If they are the same, sounds like a little more filtering is in order between B+ and B- (notice I didn't say ground) ;-)

Lewis

Hi Rich,
I have had this problem on some radios when using the solid state vibrators. I believe the high frequency switching noise is being carried into the radio on the filament line. I was able to quiet the high pitched buzz somewhat by paralleling one or both of the 0.5 mfd line filter capacitors with a high value electrolytic. Try 220 mfd, 470 mfd or 1000 mfd on either side of the line choke (L-3 if you have the schematic), or maybe on both sides of the choke. Anything over a 16 volt rating should be sufficient.

If I remember correctly, one of those values of electrolytics worked better than the others. Make sure that you install it on the INPUT line, and NOT on the secondary side of the vibrator!!

Meade

:Hi - I could use a little holiday help!! - I just restored a 1933 United Motors 980455. Complete resto with all new caps, wire, and electronic vibrator. Radio works excellent - except - with the volume turned all the way down I can hear a high pitched type buzz. Not one of those real loud buzzes just a constant higher pitched buss coming out of the speaker. At higher volumes you cannot notice it as it is drowned out by the sound of the station. I can reduce the buzz some with a cap from the 41 tube pin 6 to ground but I think that is just clipping the higher frequencies and makes the sound from the speaker a bit low and muffled. Any help or thoughts are greatly appreciated.

Meade - thanks for the info. I gave this a try but no luck. Seems I had some grounding issues at some rivets to the chassis. I've run a "ground buss wire" around to major ground points and that has helped some but still fair amount of buzz. Tried a PM speaker and that eliminated nearly all of the buzz but I'm trying to stay with the original speaker which is in perfect condition. Cannot figure out how to get this frequency out of the 6v circuit? I wonder if this is this typical of SS vibrators?

:I have had this problem on some radios when using the solid state vibrators. I believe the high frequency switching noise is being carried into the radio on the filament line. I was able to quiet the high pitched buzz somewhat by paralleling one or both of the 0.5 mfd line filter capacitors with a high value electrolytic. Try 220 mfd, 470 mfd or 1000 mfd on either side of the line choke (L-3 if you have the schematic), or maybe on both sides of the choke. Anything over a 16 volt rating should be sufficient.
:
:If I remember correctly, one of those values of electrolytics worked better than the others. Make sure that you install it on the INPUT line, and NOT on the secondary side of the vibrator!!
:
:Meade
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:
:
::Hi - I could use a little holiday help!! - I just restored a 1933 United Motors 980455. Complete resto with all new caps, wire, and electronic vibrator. Radio works excellent - except - with the volume turned all the way down I can hear a high pitched type buzz. Not one of those real loud buzzes just a constant higher pitched buss coming out of the speaker. At higher volumes you cannot notice it as it is drowned out by the sound of the station. I can reduce the buzz some with a cap from the 41 tube pin 6 to ground but I think that is just clipping the higher frequencies and makes the sound from the speaker a bit low and muffled. Any help or thoughts are greatly appreciated.