[Elecraft] K3, KPA500 - PIN Diode Failure in KPA When K3 Subrx Turned on During Xmit?

[John K3TN]

Here's the set up: K3 to KPA500 to KAT500, all Aux bus connections. Began to
have high attenuation on receive when the KPA500 was turned from STBY to
OPER. Determined by Elecraft to be a blown PIN diode, which makes sense. But
why did the PIN diode blow?

Could be that it just failed, could be I mistakenly QSYed and transmitted
with KPA at high power before KAT was tuned for new band. But I also
remember this scenario happening a few times before I noticed the RX
attentuation:

Running N1MM software in a CW contest. I was transmitting some N1MM message
and while transmitting went to hit the ESC key to do something and instead
hit the ` key, which in N1MM turns on the sub-RX in the K3.  In the heat of
a contest exchange, hard to remember exactly what happened but I think that
did cause a hard fault with the KPA. Not long after that the PIN diode was
blown.

Craig, the guy who repaired my KPA, said he didn't see how an inbound SUBRX
ON command to the K3 while transmitting cause lead to a condition where the
K3 is transmitting into the KPA while the KPA is in RX mode, but I'd figured
I'd cast a wider net to see if it triggers any possible thoughts. I'm also
cross-posting to the N1MM reflector.

John K3TN



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