[AMRadio] HQ 170A interogatory

[CL in NC]

Thought I would pick this knowledge base before digging into my HQ 170A. 

Anybody have an idea why the six meter band will break into oscillation while receiving an AM carrier?  It does exhibit some instability when aligning the radio, but when in the cabinet, it seems stable, until you try and listen to something.  Not noticeable on noise, CW or SSB, just AM.  It is like you have the calibrator on, beating against the carrier, but it is subtle, not booming.

Is there a part in the six meter section that is known to cause this?

Charlie, W4MEC in NC