[R-390] Cam Synchronization

[Craig C. Heaton]

Scott, 

If the slug screws hit the Utah plate or almost fall out of the rack; there
is a good chance some of the silver mica caps in that RF coil have drifted.
Somewhere in the middle range of the adjustment has proven on my R-390A's to
give greater sensitivity. I've had to replace some of these silver mica's.
On Chuck Rippel's web site he describes how much sensitivity is lost if the
mechanical alignment isn't correct. Get the mechanical alignment correct
first, then tackle the IF, RF, etc. 

Follow the Y2K manual step by step, hard to go wrong. Scott Secal's (sp)
description of how to reassemble the gear train might help on getting the
cams in their correct positions.

Best of luck,
Wd8kdg
Craig 

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of odyslim at comcast.net
Sent: Tuesday, September 18, 2007 1:38 PM
To: wabate; R-390
Subject: Re: [R-390] Cam Synchronization

 I would leave it alone. 1/8" is practically nothing. In fact, the person
that last
serviced the radio may have deliberately moved the cam a little to keep the
slug screws from hitting the utah plate after alignment. The slug racks can
easily compensate for 1/8 on the cam.

  SCott
 


 -------------- Original message ----------------------
From: wabate <wabate at verizon.net>
> Hi.  I'm working on a newly acquired 390A and I've started with the 
> mechanical synchronization.  I've worked on 390A's before but this is 
> the first that is slightly off sync. Four of the cams were off no more 
> than 1/8" so I decided to touch it up.  The other two cams were OK.  I 
> adjusted three but I'm stumped on the 8-16MC cam.  That cam does not 
> have a non-mar clamp on it.  Its riveted to the gear.  How do you adjust 
> that cam?  The manual does not say anything specific about that cam.  It 
> appears that the MC shaft controls it but I don't want to guess wrong 
> and adjust something that I should not.  The 8-16MC cam is off about 
> 1/8" from where it should be.  Should I ignore it?  If I try to align 
> that cam with the KC shaft, I get to the end stop before it lines up. 
> Over ten turns stop readout of the KC shaft is within spec and the 
> crystal osc. band switch is OK.  The intermittent switch drive is off 
> about one tooth from where it should be but the the six position RF band 
> switch alignment is OK.
> 
> Thanks,
> 
> Bill, K3PGB
> 
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