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

[Gerry Steffens]

The manual doesn't appear to directly address this by number but here is the
step:

"See Figure 22 and start two 6-32 X 1/4" BHMS into the 1/4" X 1/4" rigid
shaft coupling.  Place a shaft adaptor on the antenna tuning capacitor.
Slide the 1/4" X 1/4" shaft coupling on the antenna capacitor shaft and
tighten."

There is no picture showing the unassembled group and thus the shaft
adaptor.

In the parts list there is mention of a shaft adaptor part # 455-11 with a
count of 1.  This must be the critter but no data and no part number
referenced other than shown above.

Now, anybody know the difference between a GC-1 and a GC-1A?  I think the
chrome versus dull pot metal knobs might be part of it??


Gerry


Collecting & Restoring since 1959
Gerald Steffens P.E.
Oronoco, MN


-----Original Message-----
From: heathkit-bounces at mailman.qth.net
[mailto:heathkit-bounces at mailman.qth.net] On Behalf Of Philip Atchley
Sent: Monday, February 21, 2005 12:45 PM
To: heathkit at mailman.qth.net
Subject: [Heathkit] Mohican Shaft coupler, Antenna Trimmer capacitor,need
information.

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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