{Collins} More Guidance Needed on 75A-3 Alignment



Hi All:

A little more than a week ago I related the story of how my 75A-3 PTO had
shaken loose during shipment and I needed some information on how the
coupler was assembled.  Thanks to Bob and Ian from the list I was able to
recouple the PTO and get the receiver running.  Now I have another issue to
deal with: alignment.

During the process of coupling the PTO to the dial machanism, I noticed that
the variable IF slug rack and the PTO seem to be out of sync.  Using a
signal generator, I injected a known frquency (7 MHz) into the antenna
terminal, rotated the PTO shaft until I found the signal, and then turned
the dial mechanism until the frequency display read properly.  The problem
is that the signal doesn't peak where it should: the dial mechanism that
varies the IF slugs peaks the signal about 50 KHz away from where the PTO
tunes the signal.  By the way, none of the set screws that couple the dial
mechanism to the coupler or PTO shaft had come loose, so I don't think it's
simply a mechanical issue.

Here's my issue: I can easily realign the receiver, but before I do that I'd
like to know if there is something else I should look for.  After all, 50
KHz out of sync is pretty drastic.  Could the PTO have more than one
response to a signal?  I wonder if I should have rotated the PTO throughout
its entire range before I settled on the first point that heard my sig gen?
If there should be only one point that the PTO tunes a signal and assuming
that the PTO is where it should be, then would it be better to loosen the
set screws to get the two in sync or just do the alignment (which I'd do in
any case).  Suggestons?

BTW, after I get this fixed I'll be after some help with adjusting the PTO.
The tracking is way off from one end of a band to the other.  But that's a
problem for another day...

73,
Jim
WA2MER

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