My amp is the older design shipped in August, 2006 but the KPA100UPKT was
installed. If the new C31 was part of that kit it's in there but if not I
don't think it is. Question - would it make sense to tune at low power
until I figure out the problem? I'm thinking that would avoid blowing the
diodes and still allow me to use my new KAT100.
----- Original Message -----
From: "Don Wilhelm" <[EMAIL PROTECTED]>
To: "Bill Carpenter" <[EMAIL PROTECTED]>
Cc: "elecraft list" <elecraft@mailman.qth.net>
Sent: Monday, January 07, 2008 8:19 PM
Subject: Re: [Elecraft] KPA100 D16/D17 still blowing
Bill,
That is not normal - BUT -
Before I can offer a single suggestion, can you say whether your KPA100 is
the older T/R switch design or is it a KPA100 that shipped after Nov 2006?
If it is the older design, has it been updated with the KPA100UPKT - and
if it has been updated, was C31 also changed to 0.22 uf?
*If* you have the older T/R switch design, there is a possibility of a
parasitic that can show up during tuning, particularly on 40 meters. With
the new design, *if* C31 was not changed to 0.22 uf, there is a
possibility of a low frequency oscillation that shows up when operating on
160 or 80 and sometimes on 40 meters. It might be possible for an
oscillation to create a sufficiently high RF voltage to zap the diodes
during a tuning cycle of the KAT100. (Note that there are many 'ifs'
here, thus the reason for the questions to be answered - it depends on the
level of your KPA100).
If your KPA100 is the older design, I suggest the KPA100UPKT may cure the
diode zapping, but if you already have the update (including the new C31),
then there is some other problem.
73,
Don W3FPR
Bill Carpenter wrote:
Hi all,
Since adding a KAT100 to my K2/100 about a month ago D16 and D17 in the
KPA100 have blown 3 times. The first time I thought it was caused by
antenna static buildup during a blizzard but the last 2 times it happened
as the tuner was attempting to tune an antenna. Could there be problem
with the tuner that is causing this? Everything is well grounded and the
antennas are not bedsprings but a G5RV and twin sloper.
I'm getting real tired of replacing those diodes!
73,
Bill NZ0T
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