It sounds like the PIN diode switches are either stuck in the transmit
position, or the receive path has failed. Since a mechanical relay
bypasses the PIN diode switches in STBY, received signals would then get
through normally.
73,
Scott K9MA
On 7/20/2018 19:54, Jim Fitzpatrick via Elecraft wrote:
I received my new KPA1500 in mid April. After giving it a test drive
and making a few QSOs here at home in Madison I took it up to our
cabin in northern WI where it will live. I operated the Florida QSO
party with it, as well as the ARRL VHF contest with no problems. I
also made quite a few FT8 QSOs on 6 meters in casual operation. This
past weekend I went up there for the IARU contest. I started on 40
meters and noticed no problems. Note that I do virtually all my
receiving on 40 with Beverage antennas in the summer due to
thunderstorm noise. After a couple of hours I went to 20. I thought
that the band was awfully quiet and pretty dead. After a few hours I
took a break. I was working people at a fairly good rate running about
1300 watts, but signals seemed very weak. Coming back from the break
the band seemed much better. After a few minutes I noted that I had
forgotten to take the amp out of standby and was running about 30
watts. So I put the amp in the operate position and all the signals
disappeared. After a lot of putzing and futzing it appears that there
is somewhere between 20 and 30 dB of attenuation in the receive path
when the amp is in the operate position. I didn't notice it initially
on 40 because I was using the Beverages. This appears to be the case
on all bands. I am using resonant antennas and it is unaffected on
transmit. It will put out full power on all bands with a low SWR. It
doesn't matter if the tuner is in the circuit or not. So I took down
the amp and for the rest of the contest I used my old amp, a Tokyo
HiPower 550 without any problems. So I brought the whole thing back
home and set it up here. I rebooted the firmware and then downloaded
the newest firmware without any change in how it is behaving. There is
no problem with the K3 or the other amp. The K3 works just fine with
my KPA500 at home. So the bottom line is the KPA1500 has developed an
attenuation of somewhere between 20 and 30 dB in the receive path
(estimated from the S meter on the K3 assuming an S unit is somewhere
between 3 and 6 dB). I haven't done anything klutzy like leave the K3
with the receive antenna switch on with no antenna attached....I've
done this before :-). I'd appreciate any advice or ideas.
73
Jim WI9WI
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Scott K9MA
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