[ARC5] [Milsurplus] BC-348 Backlash Again

[Kenneth G. Gordon]

On 22 Aug 2012 at 12:35, WA5CAB at cs.com wrote:

> Dave,
> 
> Any anti-backlash gear and worm pair that I ever saw has several times
> the amount of rotation (throw) needed to remove any amount of backlash
> between it and its driving worm gear (pinion).  If, when preloaded,
> there is still backlash between gear and tuning knob, I can think of
> five possible reasons:
> 
> (1) loose set screws in shaft couplings or knobs.
> (2) end float in the pinion shaft bearings (if that's your problem,
> then the plastic tape must have side-loaded the pinion enough to force
> the balls to the zero clearance point of one or two of them, which
> will pretty soon quit working as the tape wears). (3) weak spring. (4)
> excessive torque required to rotate the capacitor shaft. (5) excessive
> force required to rotate the movable gear.

Dave:

Adding somewhat to what Robert has listed above, it has been my 
experience that if the tuning capacitor has a lot of drag, for any of a number 
of reasons, backlash, even with the split-gear anti-backlash units, and 
everything else (shaft couplings, end bearings) are correct, backlash will 
never be acceptable. The main reason is excessive drag in the capacitor 
itself, usually due to deterioriated lube, a misaligned main-shaft, or other 
such things.

In your case, I would, if possible, remove the main-tuning cap and check to 
see how hard it is to rotate. It should be rotatable with one finger.

Ken W7EKB