"Frank Dresser" wrote in
message ...
On Thu, 02 Apr 2009 10:52:03 -0700, Richard Knoppow wrote:

[snip]

I am beginning to suspect that H my have gotten a
lot
of defective tuning capacitors and used them by reversing
the dial
stringing as I had to.


Just to continue with the speculation, it's conceivable
that
Hallicrafters got exactly the tuning caps they wanted. A
reverse
rotation bandspread cap works well enough in the S-40A and
the reverse
rotation cap might have been necessary in some planned
S-40 variant.

[snip]

I don't think so. The knob, dial, and capacitor should
all rotate in the same direction. The dial must start at
zero beacuse that's the marked "band set" point, the
capacitor must set at minimum capacitance for the main dial
calibration to operate within the adjustment range of the
trimmer caps. The S-40A band spread capacitor differes from
the one used in the other S-40 models and in the S-20R,
which was the predecessor to the S-40 series, in that its
got symmerical band spread plates, the others have straight
line frequency plates. This means the rotor could rotate in
either direction and still have the same "law" of
capacitance variation with angle. The others _must_ turn in
one direction only. One of the things I noticed is that the
poistion of the opening in the flange of the main pulley as
shown in the stringing diagrams is reversed in the S-40A
from the position shown in the S-40 diagram. Usually,
stringing diagrams are shown for the dial being at one end
so that when you wind on the dial cord you have the stop to
work against. This is not the case in my RX. So, I think
both the stop pin _and_ the pulley were put on wrong. One
can speculate about why this was done. You may be right that
H specified these caps for some variation of the RX but
never made it. But, keep on mind that parts were evidently
in short supply when the RX was made so perhaps the caps
were used and the dial string crossed over as a work-around.
Note that one of the power resistors was made up of two
resistors in parallel, this is mentioned in the parts list
as a possibility so I am pretty sure it came from the
factory. It suggests that H could not get enough of some
parts and had to resort to work-arounds to meet production
committments.
Again, apparently all Hallicrafters business records
were long ago destroyed so one can only guess. If someone
has an original insruction manual the photos may be clear
enough to see how the cap is rigged, the stuff on line is
too low in resolution to show this. I wanted others with
S-40's of various types and vintages to have a look at what
is actually in them. What I am curious about can be seen by
just lifting the lid and seeing in wich direction the band
spread cap moves in going from minimum to maximum.
This is all probably quite trivial in the scheme of
things but sometimes its the seemingly trivial things which
are the most interesting:-)


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Richard Knoppow
Los Angeles
WB6KBL