[Milsurplus] BC-312 tuning backlash

[J. Forster]

In the early days of surplus, after WWII, there was a lot of
misinformation published, especially in the ham press.

-John

==================




> Many thanks to those who wrote to assure me that backlash is not
> a universal problem with BC-312 type receivers. I wonder what
> the 'Hints and Kinks' based their statement on. Perhaps because of
> the H&K's early surplus-era date, 1949, they had a limited sample
> to judge from?
> Thanks particularly to Dennis, W7QHO, who exactly addressed the
> issue. I repeat his comment for those on a list which may not
> receive these posts.
> -Hue Miller
>
> "Subject: Re: [Milsurplus] BC-312 tuning backlash
>
> 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 "
>
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