I have a Palomar 300a a older gentleman brought to me to try and fix for him. If you turn power on amp and amp on standby radio TX and RX good. Turn amp switch to operate and amp works fine as far as power out put but receive on radio drops down drastically . Put operate to standby and radio receive normal again. Board has three relays on it. First one switches operate , second is preamp and third tx rx standby I believe. The third switch I think should not engage until radio keyed and amp on operate but engages moment I use standby to operate. I have replaced diodes and transistors and am stumped any ideas????