Thanks to all of those who offered suggestions to remedy a Collins 
30L1 tuning problem. My main concern with the initial query was 
determining whether or not a bad tube could cause serious impedance 
mismatches that would  ultimately  effect the loading capacitor 
sequence. Some suggested changing several of the obvious parasitic 
components in the plate circuit;and only then consider the tubes for 
replacement. Cleaning up the bandswitch controlling the additional 
banks of loading capacitance  made equally good sense.  I'll do that 
and save the tube replacement for last. Again, what I found odd was 
that resonance on 80m was with minimum (zero)antenna tune capacitance; 
and on 40m there there was full loading (meshed) capacitance. I found 
that somewhat unusual for an antenna matching design. I'd expect some 
partial value of capacitance on that control. Some individuals took 
issue with the fact that I expected some detuning (or reduction of 
power) when rotating the antenna tune control. Perhaps my choice of 
words was no clear.  I mentioned the "dip" with the antenna tune 
control to indicate I was at the extreme ranges of capacitance on each 
of the two bands tested. Thanks again to all who took the time to 
share their thoughts. It was very much appreciated.  Best regards Ron 
W2CQM/3