[Milsurplus] BC-312 tuning backlash

[mac]

No, backlash not a problem except in the earliest BC-312/342 models.   
There is a large spring loaded gear behind the front panel that is  
engaged by two pinions, one that is driven by the "Fast Tuning" knob  
and the other by the "Vernier" dial.  The procedure is to back-off on  
the engagement of the Fast Tuning pinion just past the point which  
allows the spring loading on the large gear to become fully applied to  
the Vernier pinion.  This is done by means of an eccentrically  
drilled  bushing on the Fast Tuning shaft which is locked in place by  
a hold-down collar accessible behind the front panel Fast Tuning  
knob.  The two halves of the spring loaded gear must not be stuck  
together, of course, and all the gears in the chain should be clean  
and carefully lubricated.   In some cases the end loading of the  
ganged variable tuning capacitor may have to be adjusted (adjustment  
screw located in the oscillator compartment).

There is a problem with very early models where the hold-down collar  
for the Fast Tuning shaft bushing is located on the back side of the  
front panel and is not accessible for adjustment.  I have 1938 BC-342A  
like this.  :^(

Dennis D.  W7QHO
Glendale, CA

**********************
On Nov 3, 2013, at 12:21 PM, Hue Miller wrote:

> I was reading 'Hints and Kinks' vol. 4, 1949, in the 'surplus  
> conversions' section,
> about the BC-312. The article states, "the backlash problem is a  
> stickler". It
> seems to say that with effort, you can get the backlash down to one  
> division on
> the vernier dial.
> Now, I haven't used a BC-312 for 35 years, but I don't recall the  
> backlash being
> noticeable. Maybe I was just ignorant.   What is your experience,  
> and is the
> H&K comment reliable?
> tnx
> -Hue
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