hi not sure if you have fixed the radio at all but it sounds like the final or driver or both have failed , this is what gives the rf power output , these to transistors are based usually on the rear of the radio chasis most common part numbers for driver is 2sc2166 / PA is 2sc1969 you might find one or both transistors have failed and pulling the postive rail to ground rail ( hence the dimming of the radio) parts should cost around $20.00