[Elecraft] KXPA100 SN 707 Total Frustration with this Amp

Sun Mar 9 20:49:38 EDT 2014

Am I reading this correctly?  You are driving an AL80B with the KXPA100
being driven by the KX3?  That's quite imaginative if that's correct.  The
SWR fault is coming from the AL80B input circuit not your antenna (the KXPA
can't see the SWR on the other side of the AL80B).  probably something bad
in the input circuit of the AL80B causing the high SWR...

Dr. William J. Schmidt - K9HZ / J68HZ/ 8P6HK/ ZF2HZ

Owner - Operator
Big Signal Ranch
Staunton, Illinois

email:  bill at wjschmidt.com

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of rldillon at aol.com
Sent: Sunday, March 09, 2014 7:24 PM
To: elecraft at mailman.qth.net; KX3 at yahoogroups.com
Subject: [Elecraft] KXPA100 SN 707 Total Frustration with this Amp

Upfront this email is long and outlines the frustrations with this amp that
I have never encountered with another piece of new Ham Equipment in my 27
years of being licensed.

First indication of Problem:

I received this amp on 27 Feb at 10:55 when the situation started. I
unpacked the items and laid them out on the table with an anti-static mat in
place. As I inventoried the items, I discovered that I had two back plates
and no face plate. I started assembly of the amp and noticed that the hex
nut for the RS232 (PC) connector was missing. I looked in the parts bag and
it was not there either. I sent an email to parts at Elecraft and received a
phone call asking to describe what was missing. I described in detail what
was missing and received a promise that correct parts would be shipped.

Front Plate and hex nut were shipped via USPS on 3 March and received in WV
on 5 March. I installed the front plate and then opened the small envelope
with the hex nut. It was the wrong one. I sent another email to Parts at
Elecraft with an attached picture showing that the part sent was the wrong
one.

The correct part was shipped 6 Mar and received 8 Mar. I installed and
hooked up the amp today (see comments below for todays adventure).

What has really caused the frustrations with this amp.

After the weekend ARRL Contest, I hooked the amp to the KX3 per the manual
by setting Tun Power to nor and PA MODE to on. The amp immediately came to
life. I adjusted the power knob and noticed that the power was now showing
what the amp would output versus the KX3 power. There was station on 20 RTTY
that I wanted to work so I set the output power to 45 watts which would
drive the AL80B to just between 400 to 500 watts. Tuner after the AL80B is a
Palstar AT4K into a Hexx Beam with an swr of 1.2 on 20M with tuner bypassed.
I started up kcomm and entered the stations call. I heard the AL80B amp
keying each time I sent my call. I tried several times with no contact with
the station calling CQ. I keyed again and noticed that the al80B was only
showing about 30-40 watts instead of 4-500. I immediately stopped sending
call and exited kcomm, started the KXPA utility program and found the fault
table. It showed several faults for hi swr of 99.9:1. How do you get an swr
this high into
  an antenna with an swr of 1.2? I went back into the kx3 menu and turned
off PA mode. I then set kx3 power to 10 watts and keyed with amp turned off.
SWR showing on KX3 was 1.3. I turned amp on and keyed up with another fault
for Hi SWR. I did work the station with my TS590, AL80B, Palstar tuner and
hex with NO SWR problems!!

I tried more bands with the same problems. I downloaded the Beta Firmware
and new utility and updated the firmware. Same problems and results. I
swapped out the coax between the KXPA100 and the AL80B. Same results. I
swapped out the coax that came with the KXPA cable package with a known good
jumper to the amp same results. I bypassed the AL80b and Palstar tuner
direct to the hex. Hi SWR faults. I tried dipole with Palstar same results.
I added an LDG Auto tuner after amp with same results.

I reloaded ver 1.04 of the firmware and tried again same results. I also
reloaded the beta a second time.

Today I hooked the amp back up after installing the correct hex and decided
to try some more trouble shooting. Today with the PA Mode on and running the
utility software, If I uncheck PA Bypass, which comes on with equipment turn
on,  the PA Bypass comes back on. I can hear the relays clicking each time.
If I change PA Mode so I can manually turn the amp off and on the PA Bypass
works correctly. I changed the short piece of CAT 5 with a piece of fully
shielded CAT 6. Did not make a difference.

I saw on the reflector an individual having problems with tuner retuning
during a qso due to sensitive SWR . This is not my situation as mine does
not have a tuner and is a kit version. I also saw where an individual had a
problem using an LDG auto tuner. That is also not a symptom I am having as
LDG tuner tunes fine when you use at least 5 watts or so to tune.

Any suggestions would be appreciated. I have totally lost any faith or
confidence in the amp. As one of my friends told me it is probably time for
it go away.

Rich, K8VE

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