[AMRadio] NC-183D Alignment questions help


John Coleman jc at pctechref.com
Wed Sep 26 18:55:12 EDT 2007


Is the oscillator freq on the low end too high and needs to be lower or is
it to low and needs to be higher.

Some one mentioned that the oscillator may be running on the wrong side.
You may know this already but I will state it anyway, that the OSC must be
running above the RF that you want to receive.  OSC = RF + IF.  It is some
times possible to pull the OSC with the trimmer all the way down to where
the OSC = RF - IF.  This will work where you set it but it will not track as
the manufacture did not design it that way. 

Assuming that the culprit is ageing coil forms, not incorrect parts or IF
misalignment, there could be a number of quick fixes for this type of thing.
Padding capacitors can be added in series with the top end of the coils or
extra turns could be added to the coil assembly or just placed in series
with it.  I have beat up some powdered iron and put it into the coil form
with glue to lower the frequency. 

John, WA5BXO
 

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Van K7VS
Sent: Tuesday, September 25, 2007 11:04 PM
To: Discussion of AM Radio in the Amateur Service
Subject: [AMRadio] NC-183D Alignment questions help

I have a pristine NC-183D I picked up a year ago that I am finally getting 
around to.  Have replaced all the electrolytics and sound really good. 
BUT...I cannot get it to track properly as I follow the alignment 
instructions in the manual.  I can set the top frequency on each band with a

small trimmer cap (this is the oscillator coil adjustment) but then 
according to the instruction manual you adjust the low end of the dial by 
moving a wire inside an inductor, which does move the lower frequency but 
not nearly enough to get to the frequency they say you should see.  Has 
anyone else had that problem during alignment of this receiver, or am I 
missing something.  Have checked the voltages at the first and second 
converter and they seem fine and have pulled off the mica cap across one of 
the oscillator coils  (1.8 to 5 Mhz) and it checked just fine (supposed to 
be 1600 pf and reads 1615 pf).  And have substituted a different 6BE6 in the

first converter and still can't get close to proper or accurate dial 
tracking.  I am 500+ Khz off no matter what I have tried.  And thoughts on 
this one!  Thanks.  Van, K7VS

PS  I would like to hear from NC-183D owners that may have experienced this 
problem or have some thoughts about what I am seeing.  tnx 

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