[Johnson] Ranger 1 Question/Problem

[Jerry K]

If you look at the reason the VR tube gets too hot, moving R3 outside the
box doesn't do anything to change that. It's a carbon resistor that
decreases in value if it is repeatedly heated up past it's dissipation
limits. Since it dissipates about 4 watts in normal service, and since it's
a 3 watt resistor, then (duh) the limits have been exceeded since day one
from the factory. :-)  Simply changing R3 to a 5W (or better, 7.5W if you
want overkill headroom) wire wound type is the fix. Whether or not you move
it is immaterial to fixing the root problem, it just means there's another
wire to mess with going outside the VFO, a 'mod' that has no good reason for
being. The 3W carbon resistor will dissipate 4 watts (as it slowly fries to
death), and the new wire wound will also dissipate 4 watts. The wire wound,
however, unlike the carbon, will stay at 18K. No heat is added or subtracted
in the VFO compartment by changing R3 to a wire wound type.

Moving R3 out of the VFO reduces inner VFO compartment heat by 4 watts,
which appears to do nothing positive, and relocates the 4 watts to the
chassis underside, which runs very hot to start with. That makes physical
relocation of R3 more or less a useless exercise, since the VFO has been
proven to run basically forever at it's factory designed heat load, with the
exception of the R3 problem. However, relocating it doesn't actually hurt
anything, I guess, if it makes the owner feel better. Everything gets taken
to extremes in our hobby by some, so I'll bet there is a Ranger out there
somewhere with a 50W 18K wirewound bolted to the back of the cabinet, with a
fan on it.

73, Jerry W5KP


-----Original Message-----
From: johnson-bounces at mailman.qth.net
[mailto:johnson-bounces at mailman.qth.net]On Behalf Of C Eus
Sent: Friday, April 08, 2005 8:46 AM
To: Freeberg, Scott (STP); johnson at mailman.qth.net
Subject: RE: [Johnson] Ranger 1 Question/Problem


Hi Scott:
Actually, I don't think the issue is really frequency
drift as opposed to the catastrophic results of
leaving that 18k resistor in the vfo compartment. Ask
W3BYM (Tom Marcello) (?). He had this problem and
hence a large restorative undertaking that could have
been prevented with the resistor changed and outside
the box.


JMHO.
Cal, N6KYR/8
--- "Freeberg, Scott (STP)"
<Scott.Freeberg at guidant.com> wrote:
> I have a Ranger II with the resistor in the VFO
> cabinet and a Valiant 1 (same VFO design)with the
> resistor outside of the VFO cabinet.  I don't notice
> any difference in drift between the two in my casual
> AM and CW operation.  I'm happy with both.
>
> This sounds like one of those fun topics that will
> be argued forever, like the solid state rectifier vs
> tube rectifier :))))
>
> 73, Scott WA9WFA
> http://wa9wfa.home.att.net
>
> Johnson mailing list
> Home:
> http://mailman.qth.net/mailman/listinfo/johnson
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Johnson at mailman.qth.net
>



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