1939 model 39-30

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1939 model 39-30

wa2ise
Member

Posts: 77
Threads: 24
Joined: Nov 2010
City: Oradell, NJ

#9

09-20-2013, 03:30 PM

Quote:It took three #75 tubes until I found a good one that didn't cause a muffled hissing after the set played for about 5 or 10 minutes

That might have been a supersonic parasitic oscillation. A "grid stopper" resistor, around 68K, placed in series with the grid wire right at the top cap of this tube (its grid), should tame those unruly tubes you have. This resistor, in combination with the tube's stray capacitance, acts like a low pass filter to disable the oscillation.

(This post was last modified: 09-20-2013, 03:33 PM by wa2ise.)

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Messages In This Thread

1939 model 39-30 - by NostalgiaRadioTime - 09-13-2013, 11:47 PM

RE: 1939 model 39-30 - by Radioroslyn - 09-14-2013, 05:54 AM

RE: 1939 model 39-30 - by Bill Kinghorn - 09-14-2013, 09:42 AM

RE: 1939 model 39-30 - by Jamie - 09-14-2013, 01:40 PM

RE: 1939 model 39-30 - by Tom Hamilton - 09-20-2013, 10:29 AM

RE: 1939 model 39-30 - by TA Forbes - 09-20-2013, 12:14 PM

RE: 1939 model 39-30 - by TA Forbes - 09-20-2013, 12:15 PM

RE: 1939 model 39-30 - by NostalgiaRadioTime - 09-20-2013, 12:45 PM

RE: 1939 model 39-30 - by wa2ise - 09-20-2013, 03:30 PM

RE: 1939 model 39-30 - by wireless - 09-21-2013, 04:45 PM

RE: 1939 model 39-30 - by NostalgiaRadioTime - 09-21-2013, 08:45 PM

RE: 1939 model 39-30 - by NostalgiaRadioTime - 09-21-2013, 08:49 PM

RE: 1939 model 39-30 - by Electrothaumaturgist - 09-21-2013, 09:57 PM

RE: 1939 model 39-30 - by Arran - 09-21-2013, 10:00 PM

RE: 1939 model 39-30 - by Eric Adams - 09-22-2013, 10:23 AM

RE: 1939 model 39-30 - by PhilcoJohn - 09-26-2013, 07:01 AM

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