The side tone on my K2 (sn 537) has stopped working... not a peep. Also, the spot function is not audible. I have checked the "St L" (set at 50) and run it all the way up... no side tone. CW is operating properly, internal keyer or externally. Does anyone recognize this problem, or do I just go in and check voltage levels? Thanks, and 73 Dave K2YG