[Elecraft] Relay type noise with KPA500 and PR6

[Paula Uscian]

I am hearing a rapid relay-type rattling noise from my K3 whenever I transmit over 30W barefoot and the PR6 with the ACC option is connected. This wasn't happening before I added a KPA500 into the mix. I don't hear the noise when power is below 30W barefoot, nor when the KPA500 is inline.
 
I am using the KPA500 AUX cable, and the Elecraft Y cable from the K3 so I can connect both the ACC option for the PR6 and the KPA500 to the K3 ACC port.
 
I have searched the reflector for insights on this behavior and why it is happening, but not sure anything I've found applies--expept the possibility of needing to remove pin 10 from the KPA500 AUX cable--?
 
Guidance, wisdom and other assists are most appreciated. Thanks.
 
73 Paula k9ir