I have a Galaxy DX 55v cb radio...The problem I am having is that when I key the mic the radio does key up but will not modulate.I have tried several different mic's...I also have trouble receiving but if I key the mic and let off, it will hear very well for a minute or so then the receive drops back to barely audible...Any help with this will be greatly appreciated !

Sounds like somebody has tampered inside it , knocking out alignments. There is a resistor and very small transistor near back that controls transmit+receive. I don't know which number resistor it is on your model. I know where it is on Uniden/Cobra models(recommend Cobra 25ltd) Take to Cb shop or service repair place. They may help you. Just buy you a Cobra for cheaper and go with it.