I got a Bray mod 1987x. Here is the issue. I play the amp for a little while and everything is fine. After about 15 mins I get some volume drop accompanied with popping that sounds like a loose Guitar jack input (which of course its not). Then I get a screeching sound, and by this time I turn the standby switch on and all goes quiet (thankfully). I flip the standby switch off again and keep playing but the problem reoccurs after a brief reprieve.