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



Jim --

Is it possible that you created a 1/2 turn offset when you reassembled 
the coupler?

73
Bob

Jim DiMauro wrote:
> 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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Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
Sun AM Net: 29.050 Mc-1200 Central






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