[Collins] 32S-3 drive issue

[Ken Plesser]

Gentlemen:

 

A problem with a 75S-3B that someone might be able to help with.

 

When tuning up on 20 meters, full clockwise rotation of the MIC GAIN is necessary in order to get anywhere near full-scale deflection of GRID CURRENT in the TUNE position of the FUNCTION switch.  This is not a problem on any other band.

 

Similarly, full clockwise rotation of the MIC GAIN is necessary to achieve the proper level of plate current and power output on voice peaks.  In fact, full output (and appropriate ALC indications) on voice peaks is only possible with a high-impedance crystal mike. I can't get there with a lower-output ceramic mike.

 

I have replaced tubes V1 through V5 with no apparent change.

 

Any thoughts?

Ken, W3ESH