[R-390] MC/KC knob dancing

David Wise [email protected]
Wed, 4 Jun 2003 13:35:37 -0700


Excess friction in the gear train exacerbates this.
Also, the MC detent notches wear with use of
the MC knob and may simply be worn out.  It's
probably possible to re-cut them, but you have
to get them exactly 120 degrees apart to avoid
poor sensitivity on some bands due to misalignment.
IMO Collins should have used a pull-to-turn or
push-to-turn arrangement with positive locking.

Dave Wise (SWL)

> -----Original Message-----
> From: John KA1XC [mailto:[email protected]]
> Sent: Wednesday, June 04, 2003 11:06 AM
> To: R-390 reflector
> Subject: Re: [R-390] MC/KC knob dancing
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> Todd,
> there is a stainless steel "leaf" springy thing in the front=20
> of the RF deck
> which presses into the notches on the differential gear plate=20
> (I think),
> thus holding it in place when the KC knob is tuned.
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> If the tension is insufficient it will allow slippage; the=20
> tension is an
> easy thing to adjust. On the other hand the spring could be=20
> cracked; I had
> this problem in my EAC and replaced it.
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> Not a big problem, but if the MC knob turns it means the cams=20
> are moving too
> which will affect the RF alignment.
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> John
> KA1XC
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> ----- Original Message -----=20
> From: "Todd Bigelow - PS" <[email protected]>
> To: <[email protected]>
> Sent: Wednesday, June 04, 2003 1:11 PM
> Subject: [R-390] MC/KC knob dancing
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> > Okay, now for something completely different....
> >
> > Can someone tell me what the correct term is for the phenomenon
> > exhibited when the MC knob slowly turns when the KC tuning knob is
> > turned? I noticed this the other day on my Teledyne which has been
> > sitting for a while unused. Also, what causes it? I know=20
> the gears are
> > obviously crudded up since I've not yet done the complete=20
> tear-down, but
> > specificially is seems like a type of clutching taking place?
> >
> > Yep, I know - it's been mentioned before. I've just=20
> forgotten. They say
> > the mind is the second thing to go, can't remember what the=20
> first one
> > is.....
> >
> > de Todd/'Boomer',  KA1KAQ
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