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model 20 hum (detector circuit?)
#42

(10-29-2015, 07:31 PM)radiohenry Wrote:  Hi Tubesforme,
    I would like to suggest reviewing the rebuild of the filter block. I suspect there in lies the problem. Certainly it can be rebuilt using electrolytics  however the original did not have electrolytics or if I recall correctly .22uf.
  The filter block used two 1.0 uf , one 1.5 uf and one .13uf and if I read this correctly pin #1 was the common ground.
  On the last 20 that I rebuilt the filter block I removed the old components and using non electrolytics wired all the components inside the old can to the terminals indicated on the filter block diagram . When I finished replacing all the other caps and resistors it played like a new radio.
   Just my thoughts after I was fortunate to have an excellent experience in the rebuild of a model 20.
                                                    Good luck,
                                                             Henry

Henry,  I did not use electrolytic's. I used the original values and they were all new Metalized Polyester rated at 630V. The filter uses two 1uf, one 1.5uf and one .13uf (1-.1 paralled with 1-.033) The 1.5uf is the AF supply filter and yes it has been changed twice. I would never use electrolytic"s to rebuild a capacitor that originally used paper type.Tubesforme


Messages In This Thread
model 20 hum (detector circuit?) - by Tubesforme - 10-19-2015, 01:11 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-19-2015, 06:23 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-20-2015, 10:01 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-25-2015, 10:57 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-25-2015, 11:39 AM
RE: model 20 hum (detector circuit?) - by morzh - 10-25-2015, 11:08 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 10:18 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 10:34 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 11:24 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-27-2015, 08:43 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-28-2015, 11:52 AM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-28-2015, 03:36 PM
RE: model 20 hum (detector circuit?) - by Tubesforme - 10-29-2015, 07:44 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-30-2015, 06:13 PM
RE: model 20 hum (detector circuit?) - by OZ4 - 10-31-2015, 10:40 AM
RE: Low continual hum in model 21 - by Tubesforme - 10-23-2015, 11:19 PM



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