[drakelist] TR-7 Transmit / Receive Problem

[RadioMB]

Hello Drake Guys,    I am new to the group. I have a problem I hope someone can help with. My TR-7 (that I bought new) has an intermittent receive/transmit problem. When I push the PTT on the sideband mode the TR-7 will not go into transmit. If I try closing the key in CW mode again it will not go from receive to transmit (the sidetone monitor does come on). The relay does not close. This goes on for a while then the radio will work for a number of weeks, then the problem happens again. The WEIRD part is that if it stops working on 14, 7 or 3.8 mhz I can go to 21 or 28 mhz and  it will work there. If I go back and forth, 14 mhz or less will not work and 21mhz or higher will work. This has always been the case. The TR-7 will then work fine for a few days or weeks then go into this cycle again. I have tried different microphones including a new one. Do you think it is the relay, if so why would it always work on 21 mhz or higher. Any ideas would be greatly appreciated.   73  Mike  WD5GLW