PRESIDENT WASHINGTON MIC PROBLEM

[CB RADIO FREQ]

Hello everyone I have a president Washington cb base (5 pin mike) that sounds like it gets feedback when transmitting. I have disconnected the speaker and it still does it. The radio has two mics wired for it but both do the same thing. I have also tried grounding the mic to the radio and that worked for a while but then stopped working later. If it helps It has an MB-8719 PLL. If anyone knows how to fix this problem any help would be appreciated. THANKS