model 20 hum (detector circuit?)

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model 20 hum (detector circuit?)

Tubesforme
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Posts: 107
Threads: 20
Joined: Feb 2015
City: Los Angeles, CA

#52

10-30-2015, 07:04 PM

(10-30-2015, 06:13 PM)OZ4 Wrote: Maybe there is some leakage between the windings of the power transformer.

With the power off lift the #26 the 1400 ohm resistor then check the resistance from center tap winding #5, (that powers the filimants of the 71s) and the center tap #6 of the power transformer.

With #26 resistor lifted and even with all the tubes in place there should be no continuity between these two points. If there is that could cause AC hum.

I tried this and there is no reading when 1400 ohm resistor is disconnected. My manual calls the resistor part #25. #26 is the main filter capacitor pack in my schematic, from Philco. By the way, I also tried replacing the 2.5V winding with another transformer and the hum remained so it isn't coming from the 2.5V winding either.

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Messages In This Thread

model 20 hum (detector circuit?) - by Tubesforme - 10-19-2015, 01:11 PM

RE: model 20 hum (detector circuit?) - by Steve Davis - 10-19-2015, 03:40 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-19-2015, 06:23 PM

RE: model 20 hum (detector circuit?) - by Steve Davis - 10-19-2015, 07:03 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-20-2015, 10:01 AM

RE: model 20 hum (detector circuit?) - by mikethedruid - 10-24-2015, 07:04 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-24-2015, 09:24 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-27-2015, 03:58 PM

RE: model 20 hum (detector circuit?) - by Alan Douglas - 10-24-2015, 07:23 PM

RE: model 20 hum (detector circuit?) - by mikethedruid - 10-24-2015, 11:48 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-29-2015, 06:21 PM

RE: model 20 hum (detector circuit?) - by Steve Davis - 10-25-2015, 12:01 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-25-2015, 12:46 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-28-2015, 08:14 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-30-2015, 07:30 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-25-2015, 10:57 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-25-2015, 12:40 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-25-2015, 11:39 AM

RE: model 20 hum (detector circuit?) - by Kenneth F. Besso Jr. - 10-25-2015, 08:01 PM

RE: model 20 hum (detector circuit?) - by morzh - 10-25-2015, 11:08 PM

RE: model 20 hum (detector circuit?) - by Steve Davis - 10-26-2015, 08:38 AM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-26-2015, 10:18 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-27-2015, 12:14 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 Tubesforme - 10-27-2015, 12:12 AM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-27-2015, 08:43 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-27-2015, 11:38 PM

RE: model 20 hum (detector circuit?) - by Steve Davis - 10-28-2015, 12:25 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-28-2015, 01:12 PM

RE: model 20 hum (detector circuit?) - by Ron Ramirez - 10-28-2015, 02:34 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-28-2015, 08:07 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-28-2015, 11:52 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-28-2015, 01:08 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-29-2015, 07:50 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-28-2015, 03:36 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-28-2015, 08:03 PM

RE: model 20 hum (detector circuit?) - by Ron Ramirez - 10-28-2015, 09:10 PM

RE: model 20 hum (detector circuit?) - by radiohenry - 10-29-2015, 07:31 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-29-2015, 07:44 PM

RE: model 20 hum (detector circuit?) - by LASJayhawk - 10-29-2015, 07:57 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-29-2015, 10:10 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-30-2015, 07:21 PM

RE: model 20 hum (detector circuit?) - by LASJayhawk - 10-29-2015, 10:36 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-30-2015, 01:28 PM

RE: model 20 hum (detector circuit?) - by LASJayhawk - 10-30-2015, 03:29 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-30-2015, 03:34 PM

RE: model 20 hum (detector circuit?) - by klondike98 - 10-30-2015, 04:24 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-30-2015, 06:13 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-30-2015, 07:04 PM

RE: model 20 hum (detector circuit?) - by OZ4 - 10-31-2015, 10:40 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-31-2015, 02:06 PM

RE: model 20 hum (detector circuit?) - by Ron Ramirez - 11-08-2015, 10:28 PM

RE: model 20 hum (detector circuit?) - by Tubesforme - 11-09-2015, 08:11 PM

RE: Low continual hum in model 21 - by Steve Davis - 10-23-2015, 10:34 PM

RE: Low continual hum in model 21 - by Tubesforme - 10-23-2015, 11:19 PM

RE: Low continual hum in model 21 - by Steve Davis - 10-24-2015, 12:01 AM

RE: model 20 hum (detector circuit?) - by Tubesforme - 10-24-2015, 06:50 PM

Need correct voltages for det and af model 20 - by Tubesforme - 11-07-2015, 05:54 PM

RE: Need correct voltages for det and af model 20 - by morzh - 11-08-2015, 12:09 PM

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