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[TenTec] 238B Tuner problems

To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Subject: [TenTec] 238B Tuner problems
From: "Natan Huffman" <W6XR@Frontiernet.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Wed, 14 Jul 2010 20:38:31 -0400
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Dear Friends,
Today, I resolved a problem encountered with my Ten Tec 238B antenna tuner.
A week ago, my 238 started to misbehave and presented with what appeared as
an "open" in the tuner.  No discernable flash over had taken place as the
problem appeared spontaneously without any noise, smell or any indication
trouble was brewing.  The VSWR meter stopped working and no RF was getting
through to my Array Solutions Power Master residing after the tuner in the
RF chain.  
This morning a telephone call to John at mother Ten Tec ended up with
instructions to send it home to be subjected to proper trouble shooting,
however, to do that would involve being off the air for longer than what I
wanted to be.  Therefore one last attempt to ascertain the problem and at
Ten Tec Johns suggestion, I inspected all the wafers on the switches inside.
All the tabs were there and none showed wear at all.  Finally, I became
suspicious of just where the RF was going because using my #2 lead pencil I
could see it certainly was not getting to the output SO239 as it should.  It
was easy to draw a spark up to the roller at the variable inductor but no
spark at all anywhere on the body of the inductor.  The wire wrapping around
the inductor body was void of any corrosion or flash indication.
Having nothing to loose, I grabbed the can of contact cleaner and doused
both the wheel and all the wire on the inductor form.  While still damp, a
cotton cloth was used to wipe off the excess contact cleaner.  My suspicion
was confirmed as after the cleaning of the inductor and its little wheel,
all was well.  It became easy to get a 100 watt spark with the lead pencil
on the body of the inductor, the VSWR meter started working and the Power
Master showed RF just the way it should.  A few hours post, the 238 is doing
everything it used to do prior to becoming symptomatic.
I suppose the moral here is to clean the inductor and its little wheel
because even if it looks clean, enough crud does form to insulate the wheel
from the wire on the form.  Perhaps others have found this same problem
before.  It's very nice to avoid a trip to mother Ten Tec and its associated
cost and inconvenience.  Using a wooden lead pencil for RF sniffing is only
allowed if you are into boat anchors and have been licensed over 40 years.
A mechanical pencil's use can be downright dangerous so only use a wooden
Natan W6XR
Freeville, NY
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