10-10-2026, 11:58 AM
Hi Dan,
https://www.nostalgiaair.org/models/Stro...o-1500.htm
Probably one of the hardest problems to solve. You work to get the thing to oscillate and heterodyne then it goes crazy. So the oscillation is probably there all the time but you can only hear it when the IF beats with it and produces the audible squeal. Because it's a feedback circuit and involves the IF and oscillator, the first thing to check is your work around the AVC, from the top of the volume control to the antenna. There's an rf pi filter (probably a couplette unit) on the secondary of the second IF and a 470pf mica(?) cap on pins 2 to 7 of the detector that can be checked out. Also the oscillator circuit component connections, there may be a cold solder joint. Did you clean the tube pins? Any connection that may be floating, like the leads of the AVC cap.
https://www.nostalgiaair.org/models/Stro...o-1500.htm
Probably one of the hardest problems to solve. You work to get the thing to oscillate and heterodyne then it goes crazy. So the oscillation is probably there all the time but you can only hear it when the IF beats with it and produces the audible squeal. Because it's a feedback circuit and involves the IF and oscillator, the first thing to check is your work around the AVC, from the top of the volume control to the antenna. There's an rf pi filter (probably a couplette unit) on the secondary of the second IF and a 470pf mica(?) cap on pins 2 to 7 of the detector that can be checked out. Also the oscillator circuit component connections, there may be a cold solder joint. Did you clean the tube pins? Any connection that may be floating, like the leads of the AVC cap.
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