I'm trying to track down a problem with a Cobra 40 Plus that I acquired for free. It's putting out a 1.62Khz tone on both transmit and receive. I am unable to detect the tone on pin 6 of the audio amplifier, which is supposed to be input, but I am getting a strong tone on pin 2, which according to the datasheet is a bootstrap pin. The big strangeness is that when I lift pin 6, I get no tone, but I detect no tone on pin 6 whether it is lifted or not. I also get no tone on pin 2, or anywhere else I can detect. I am having other problems with the radio as well, but I am not sure they are all related. The chanel display does not light up, the signal strength indicator lights don't light up, and the final is getting extremely hot, even when not in transmit. A wild guess would say the audio amplifier IC might be the cause of the sound problem, but I don't see how that could be causing the rest of my problems, and experience tells me that it is usually a single failure that either causes all the problems, or it causes a cascade of problems that cause all the problems. Any ideas of where this tone might be coming from based on the symptoms would be great.