[Test-Equipment] Using an HP 331A Distortion Meter

[Barry]

It doesn't appear these are anything but ordinary dual-concentric pots (one 100-ohm and one 3k-ohm) in series for a total range of 0 to 3.1k ohms.  If I have to resort to a replacement, this shouldn't be too difficult to find (or make some kind of work-around).  They're just pretty touchy at this point and I would like to smooth things out just a bit.

Thanks again,
Barry - N4BUQ

----- Original Message -----
> From: "Dale H. Cook" <radiotest at plymouthcolony.net>
> To: test-equipment at mailman.qth.net
> Sent: Thursday, September 4, 2014 2:04:53 PM
> Subject: Re: [Test-Equipment] Using an HP 331A Distortion Meter
> 
> At 10:57 AM 9/4/2014, Barry wrote:
> 
> >Does anyone have experience cleaning/replacing the balance pots?  Mine are
> >very touchy.  They appear to be the sealed type and I realize I can most
> >likely pop the back off the piggy-backed one, but not sure about the
> >"front" one and I'm wondering if I'm opening a can-of-worms with this.
> 
>  From the parts list this dual control was made by Beckman. Open the 331A up
>  and see what it looks like physically. Odds are good that you can find a
>  suitable replacement. Other manufacturers made dual controls as well - I
>  have some Allen-Bradley Type J examples of dual controls that were used in
>  other instruments but are the wrong values for the 33nA series.
> 
> In the 332A and 334A noisy balance pots are not as much of a nuisance because
> with those DAs you just want to get the balance relatively close in manual
> mode, then switch to automatic mode and let the instrument finish the
> nulling.
> 
> Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA
> http://plymouthcolony.net/starcity/radios/index.html
> 
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