This morning I put a reduction drive onto the main tuning cap of my 6U8 Mate for the Mighty Midget receiver. Before I had been directly turning the 35 pf variable cap. The tuning rate was a bit too high for easy tuning of SSB stations. This drive went in nicely and it does reduce the tuning rate considerably, but it feels a bit tight. Is there anyway to loosen up one of these drives?
Twenty or thirty years of tuning across the bands should loosen that up quite nicely.
ReplyDeleteHook a drill to it and spin maybe adding some oil if there's such a place. That's a way of exercising it, but I suspect the drive doesn't want too much wear.
ReplyDeleteOne could just put a small variable in parallel for a fine tuning control.
Michael
Hola N2CQR,
ReplyDeleteThe last thing you want to do is add oil to the drive -- I ruined a good drive that way -- it was so slick that it turned but would not turn the capacitor. What you may actually have is an alignment problem in that the mounting is such that you are placing torque on the shaft and it feels stiff. I suggest you remove the dial and slightly enlarge the two mounting holes on the dial escutcheon so that when you reassemble the mechanism that you tighten the coupling to the capacitor shaft and then hand tighten the two bolts that mount the dial mechanism face to the front panel. You should now see that the dial turns more freely. The Oren Elliot is a better mechanism.
In addition to the concentric alignment issue that Pete mentioned, you may check to see that the panel is perpendicular to the variable cap shaft. If not perpendicular, a twisting force may be placed on the reduction drive making it stiff. You may be able to have the mounting bolts loose and have reasonable turning force. As you tighten the bolts, the force to turn the knob increases. Bending the panel mounting or adding some shims to the drive mounting may address the problem.
ReplyDelete