I started the CQ WW Phone contest and the 3rd contact told me that my Transmit audio is breaking up.I switched to a dummy load and started to monitor my TX audio with a headset, sure enough it was breaking up. I plugged in the Heil Headset microphone to the same jack on the rear of the K4 and had the same problem. I cleaned out the jack on the K4 with contact cleaner and that was not the problem.

I built an adapter for the front jack (8 pin round connector) and plugged the mic into the front jack, the problem cleared up. I went back to the contest but I was bothered by this problem.

On Monday I plugged into the rear jack and monitored the break up. If I turn off the preamp the break up stops. I emailed Elecraft and explained my situation. Doug at Elecraft answered me and asked for a recording of the problem, so I emailed a MP3 file. Later that day I received an email to check for RF leakage. I was transmitting with only 5 watts and did not see RF on the field strength meter. 

The K4 has menus to monitor voltages, I noticed that on TX the input voltage drops to 10 volts. A BAD power supply! I changed the power supply and had 13.7 volts at full power and the TX audio sounded great. Why this happens only on the rear mic input is a mystery for Elecraft to figure out. I did let Doug know my solution and he thanked me.

That's how I spent my Monday after CQ WW.

One last thought the bad power supply maker will go nameless but they have 3 letters in their name and are out of business from Starkville MS.

73,

Robert "Bob" Pantazes, W2ARP