[R-390] Frequency alignment R-391

[Fred Moore]

Yes.  In my case I use a Weller soldering gun, but carefully, keeping it
moving until the lid lifts off.  But I have to admit to having no luck putting
it alo back together.  

Let me suggest another approach that doesn't involve taking to crystal apart
to move it 3 KHz.  Try paralleling a fixed capacitor across the trimmer.  But
what size?  What is the value of the trimmer and what is its adjustment range?
 That will help you guess.  Use an NPO ceramic or a mica.

-Fred

------ Original Message ------
Received: Mon, 28 Sep 2020 05:32:28 PM GMT
From: Bill Cotter <n4lg at qx.net>
To: fred_moore at usa.netCc: Collins R-390 HF Receiver List
<r-390 at mailman.qth.net>
Subject: Re: [R-390] Frequency alignment R-391

Mack,

As a last ditch effort, you might try opening the 
crystal holder and adding pencil lead marks 
around the round crystal element. This might 
lower the crystal frequency by providing 
additional mass to the element. Keep adding on 
both sides until the desired frequency comes into view.

I put crystals in a vice, pins clamped. Then, use 
a heat gun to melt the can sealing solder, and 
pull the can off with pliers.

I also have a homebrew crystal test instrument 
that connects to a counter and simulates the 
correct pF capacitance for crystal "tuning".

When you get it where you want it, seal her back up.

Best wishes - 73 Bill N4LG




At 10:49 AM 9/27/2020, you wrote:
>I have a R-391 that is about 3 kc high on 4 Mc. 
>I’ve tried adjusting the 1st crystal 
>oscillator variable cap but that won’t move 
>the crystal far enough. The same is true at 3 
>Mc. Any suggestions? I have restored at least a 
>dozen R-390a’s to factory specifications. I 
>have several ideas I could try but want to get 
>the collective wisdom of this group 1st please. 
>73, Mack W4AX -- 73, Mack W4AX 
>https://www.qrz.com/db/W4AX 
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