Mike, Try this, if you haven't already: http://www.ecse.rpi.edu/courses/CStudio/ham_radio_docs/HDR-300/HDR-300A.pdf About page 5.... If'n you've got the switch, well, enough said. If you don't have the switch it's gonna cost you $$ for the new circuit board. 73 es GDDX K9WN Jake