[Elecraft] KPA1500 problem

[K9MA]

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

k9ma at sdellington.us