Have you adjusted the squelch via the trim pot on the front of the radio? Its a bit sensitive....
Any queries I've made have been through their aol address which is
tkmradios@aol.com. Dale has always replied the same day.
I rearranged my panel so I no longer have the TKM in the panel but its been trouble-free. One thing I did not like about it was the fixed squelch.
I do have the repair manual and its quite detailed with test procedures. Any avionics shop with the manual would be able to work on it.
Regards,
Bob