[Boatanchors] Heathkit LMO Linearity

[Mark V Johnson]

Team,

 

I have an SB-310 receiver with what I believe is the "newer" style LMO in
that it as a 6CB6 tube and a three; vs. four, terminal connection strip on
the back. I have the radio working - after many repairs - but the LMO is not
linear and at the midpoint between each 100khz point, the dial is not
tracking at all. I have the LMO out of the receiver and connected to
external power supplies and I can see with a freq. counter, the LMO is not
linear. 

 

Is there a way to improve / fix this problem? Also, what is the purpose of
the small trimmer capacitor on the rear of the LMO? Was it used at the
factory to set calibration or does it affect the linearity? 

 

I have a replacement LMO I can install - came from an SB-400 - and it works
better, but it is not the LMO the SB-310 came with. It; my possible
replacement LMO, is the older style and uses a 6AU6 and has the 4 terminal
strip on the back. 

 

Suggestions as to how to adjust / fix the linearity?

 

Many thanks!

 

Mark V Johnson

VE3LU.