[Heathkit] Mohican Shaft coupler, Antenna Trimmer capacitor, need information.

[Edward B Richards]

Hi Phil. If you will tell me the diameter of the two shafts and how close
they come to meeting, I can make you a coupling on a metal lathe
........gratis.

73, Ed Richards K6UUZ


On Mon, 21 Feb 2005 18:45:26 -0000 "Philip Atchley"
<beaconeer at sbcglobal.net> writes:
> Hi,
> 
> Today I thought that perhaps I'd go ahead and do an RF alignment of 
> the 
> Mohican that I've been overhauling (the set now plays pretty good).
> 
> Anyway, I noticed that the Ant Tuning control seemed quite stiff and 
> 
> seemed to turn a 'little' easier over part of the range.  
> Examination 
> disclosed the following.
> 
> 1.  The Ant Trimmer capacitor has a shaft smaller than the standard 
> 1/4 
> inch shaft.
> 
> 2.  The shaft coupler is the standard 1/4 inch to 1/4 inch aluminum 
> job 
> with two setscrews (1 each end).
> 
> 3.  The shaft to the front panel knob is a standard 1/4 inch 
> phenolic or 
> similar material.
> 
> 4.  The specified trimmer capacitor for this circuit is 3 to 20 pF, 
> Part 
> Number 26-24.  This one has about 20 plates with a printed P/N of 
> 20M11. 
> It DOES have the correct rectangular threaded section to fit the 
> hole. 
> But it seems to have far more plates than 20pF would indicate.
> 
> 5.  The "binding" is occurring because when you tighten the setscrew 
> 
> down on the capacitor end of the coupler, the tuning capacitor shaft 
> 
> isn't centered in the oversized hole, so the phenolic shaft isn't 
> lined 
> up with the front panel.  This causes the entire thing to twist back 
> and 
> forth as you tune.  It also somewhat displaces the bracket the 
> capacitor 
> is on during part of the rotation.
> 
> FIRST:  A QUESTION.  Does anybody know if that 1/4 inch coupler was 
> the 
> "standard" for this receiver.  The limited parts list from BAMA 
> doesn't 
> show that part.
> 
> NEXT:  If somebody has a Mohican and it's not too inconvenient, 
> could 
> they look at the Antenna trimmer capacitor, and perhaps the coupler 
> and 
> see if it fits the descriptions I've given here.  I don't want to 
> proceed with alignment until I know everything is "right". IF the 
> capacitor DOES have too many plates/capacity I can always put a 
> series 
> capacitor in the circuit to reduce it's range (right now it seems 
> like I 
> have to fully open the plates to get it to align).
> 
> FINALLY: I figure that if all else fails, I can fill part of one end 
> of 
> the shaft coupler (side opposite of the setscrew) with JB Weld, let 
> it 
> set up and then "file to fit".  I DON'T have the shop facilities to 
> make 
> a correct coupler or bushing to fit.
> 
> It's been a lot of work, but when it's finished I THINK that it is 
> going 
> to be one nice Mohican, just like new. . .
> 
> 73 de Phil,  KO6BB
> http://www.geocities.com/ko6bb/
> Merced, Central California, 37.3N  120.48W  CM97sh 
> 
> 
> 
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> 
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