[R-390] Pulling crystal frequency in R390A

[Roger Ruszkowski]

Fellows,

I was reading  Bob Camp's reply to Nelson Gietz and I am reminded that these receivers are not as exact as we expect.

Back when you first rocked the signal generator into the 455 KHZ crystal in the R390 R390A IF deck.
Then you zeroed the BFO against the signal generator.
Then you peaked the IF deck for the best band pass. 
You had a signal generator and two meters to get the repair and alignment complete.

And that was 455 in your receiver.
Crystal were as good as it gets. There was no need to try and pull a crystal on frequency. 
You did not possess any test equipment that would let you discern if a circuit was more of less exact before or after adjustment.
Your crystals were OK or you went to a swap party.
Back then new crystals were in supply and parts were replaced as needed. 
I know we now have frequency counters and would like every thing down the line exact.
However some times just doing it as was originally done is still good enough.

Then again crystals do get to far out of bounds and new parts are in order. 
But 80 hertz is well within bounds.

This is military precision for you. Print it to the decimal point. Measure it with a micrometer. Mark it with chalk. Cut to size with an Ax. 
The book and life in the field on the bench is quite different.

You do not really tune L503 for the 1Khz bandwidth.
You use a convoluted process to find some adjustment range within which L503 should be adjusted to center within.
Your receiver could be operating just fine.
Believe that what you read is not always what needs to be done to get the job done.
I send you to the Pearls of wisdom at R390.net for more help with the alignment problems of the IF deck.

 Nelson Gietz wrote his problem looks like C524 may have drifted low over the past 60+ years. 
 My math (?) suggests even a 1 pf change in it could swing the LC circuit by up to 3 kHz.
 I might try to change some lead dress. Nelson

Nelson, Just change out C524. Off the shelf caps will vary a Pf or two. A couple swaps and you will get a new cap that is with the tuning range.

Respectfully

Roger Ruszkowski