[Boatanchors] Oscillation in Hammarlund HQ 170A

[John King]

I pulled an HQ 170A off the shelf to pair up with my HX 500 and found that the HQ 170A develops an oscillation of about 750 cps when the audio gain is turned up past half scale. The tone is a guess as to frequency. The controls and switches are in the range of normal operation.

I had an HQ 180AX that did the same thing and I never found the cause. The oscillation was not as bad with the HQ 180AX.

Have any of you experienced such an oscillation in a Hammarlund receiver of this series?

Your input and suggestions will be greatly appreciated. I have cleaned the tube sockets but have not taken it out of the cabinet to clean the switches.

thanks for taking a look and thinking it over. 73, John, K5PGW