[Johnson] Kit wiring instructions for Johnson Valiant

[Glen Zook]

There have been a number of experiments concerning the placement of this resistor.  Most have found that putting it outside of the VFO compartment actually affects the stability of the VFO in a negative manner.  The VFO temperature compensating capacitors were chosen to include the effect of the heating caused by the 18K ohm resistor.  When the resistor is put outside of the compartment it takes longer, in some situations never, for the temperature to reach the conditions at which the compensation capacitors were calibrated.

Of course, the choice of where to locate this resistor can only be made by the person doing the modification.  However, the previous experience of others should be considered.
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Jerry K <w5kp at hughes.net>
To: johnson at mailman.qth.net 
Sent: Thursday, January 19, 2012 11:07 AM
Subject: Re: [Johnson] Kit wiring instructions for Johnson Valiant
 
While you're in there, don't forget to replace the famous 18K 
"Chernobyl" dropping resistor with a 5 or 10 watt power resistor mounted 
OUTSIDE the VFO box. Mouser sells nice compact power resistors for 
replacements.

Stu is right about the front panel, so unless you just HAVE to pull the 
front panel for other reasons, on most of the half dozen or so I've 
overhauled I've been able to get away with just removing the side 
plate--a little tougher access and requires some extra finger gymnastics 
during component replacements, but not all that bad, and far less 
dangerous to the one irreplaceable part on the Ranger--the ultra-fragile 
and brittle "flex" (ha!) insulated tuning shaft coupler behind the front 
dial. Also, mount a couple of fuses inside the rear wall of the chassis 
(Radio Shack sells a little plastic 3AG dual-fuse mount that fits 
nicely) and replace that Rube Goldberg fused power plug and cord with a 
standard three-wire grounded plug and cord. Easy to do while you have 
the little beast upside down on the bench during recapping.

I believe the little Ranger is the best small boatanchor ever built... 
Have fun!
73 Jerry W5KP


On 1/19/2012 8:42 AM, Jim wrote:
> I second the use of AD5X's very useful documents.
> While you have the VFO exposed, replace the mica capacitors and check the
> resistors.
>
> Jim
>
>> Suggestion:
>>
>> Don't skip getting the .pdf on front panel removal, read it a few times,
>> and
>> then be VERY careful not to put any side pressure on the flex coupling
>> during the r&  r process.  It sooooo easy to destroy the phenolic wafer in
>> that coupling, as it has been severely cooked/dried out over the last 45
>> years and will now be quite brittle.
>>
>> Finding a suitable replacement is a chore.  I even tried to repair/rebuild
>> one from one of my Rangers, but  the material I used wasn't really thin
>> enough, so it wasn't really a 'flex' coupling any more when I finished.  I
>> was a lot more careful with the Pacemaker and the Valiant and managed to
>> keep the couplings intact..
>>
>> 73 de Stu W7FE
>> Henderson, NV
>>

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