[Hallicrafters] Grommets for tuning caps

[John Hurst]

I suspect that mounting the capacitors firmly at the front with a grommet in
the rear is to prevent any bending or twisting of the chassis from getting
transmitted into the capacitor frame. This should help mechanical stability
to some degree. The weaker (cheaper) the capacitor's frame the
more this would be necessary. Hallicrafters receivers are not known for
their mechanical stability, I'm sure they'd be a lot worse w/o the rear
grommet. I remember having to be very careful to not bump my operating table
with its S-40A when I was (kid) novice, especially on 15!
John, KU6X (ex Kn6SMD)
----- Original Message ----- 
From: "Mark Shaum" <k9tr at dtnspeed.net>
To: <hallicrafters at mailman.qth.net>
Sent: Monday, February 02, 2004 6:26 PM
Subject: Re: [Hallicrafters] Grommets for tuning caps


> ----- Original Message -----
> From: "Roger D Johnson" <n1rj at adelphia.net>
> >
> > I'm not sure exactly what function these grommets served. All of the
> > high end receivers I've seen have the tuning capacitor bolted firmly
> > to the chassis. I replace the old grommets with a stack of washers the
> > same thichness.
> >
> > 73, Roger
>
> I have several low to mid range receivers of various brands with the
> tuning capacitors mounted on shock mounts of some form.  On the SX-43
> that happens to be open in front of me, the main tuning capacitor is
> shock mounted but grounded to the chassis with several copper straps.
> The bandspread capacitor, however, is firmly bolted to its subchassis.
>
> I surmise that the shock mounts are to minimize microphonics and/or
> assist with control of backlash in the tuning mechanicals.  One little
> All American Five genre set I have with a built in speaker howled like a
> banshee when I tightened up the screws going through the (dried out)
> rubber grommets a bit too much.
>
> 73! - Mark
> ------------------------------------------------------------
> Mark Shaum K9TR
> email: k9tr at dtnspeed.net
> http://www.qsl.net/k9tr
> ------------------------------------------------------------
>
>
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