[Milsurplus] BC-342N Volume Control

[WA5CAB at cs.com]

Mark,

I just removed the VOL knob from a BC-312 here to be sure memory was correct. 
 The knob has a brass core that the bakelite was molded around.  The setscrew 
hole is tapped through the brass.  The panel face of the bakelite has three 
tapped holes (probably #3-48 but I didn't actually check as it doesn't matter 
to your problem).  The dial graduations are on a disk (skirt) that is slightly 
coned and attached to the face of the knob with three screws.  First thing you 
do not want to do is to try to remove the knob by pulling or prying on the 
skirt.  99 and 44/100% probability that you will ruin it.

The knob is, as you assumed before it wouldn't come off, held onto the solid 
potentiometer shaft by the single setscrew.  What's happened is that 
tightening the screw has raised a burr on the shaft.  Someone before you tried to 
remove it and twisted the knob with the shaft locked by the stop at one end of 
rotation.  So there is now a circumferential groove cut in the brass.  The knob 
will rotate but won't come off.

Pull lightly on the knob and rotate it CCW until the zero lines up with the 
line on the panel.  The setscrew hole is now probably over the burr (I'm 
assuming you already completely removed the screw) unless the last person to tighten 
the screw didn't have the knob in the right position.  Push the knob sideways 
toward the screw hole and pull hard.  You might be able to get it to move and 
come off.

If not, you are going to have to make or modify a guillotine puller that fits 
the reduced knob diameter just above the skirt.

In a message dated 9/25/2008 9:32:45 PM Central Daylight Time, 
mark.k3msb at gmail.com writes: 
> One evening after the local radio club meeting,  one of the members
> says he something in his trunk that I may be interested in.  A nice
> BC-342-N followed me home that evening.  The guys uncle had passed
> away, and he used the 342 fairly regularly until his death.  Nice
> condition inside and out (although I could do without the SO-239 below
> the band change knob).   It works,  but needs restoration throughout.
> 
> The Volume knob is scratchy, so I thought I'd remove it and hit it
> with some DeOxit.  Seemed simple enough.
> 
> I feel embarrassed to ask this, but how the devil do you get the knob
> off?   The screw comes out nicely,  but the knob will not budge, and I
> don't want to force it.   I tried putting a few drops of WD-40 in the
> hole, but that didn't work.  With the screw loose, the knob (not the
> shaft) will turn freely, so something's holding it in.
> 
> Second,  looking at the pots,  I don't really see a way to get any
> DeOxit inside;  not any large openings near the lugs (which I guess
> makes sense as it was intended to operate in harsh environments.  So,
> suggestions on cleaning it?
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480   
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