Weird La3a problem, please help.
I have two old La3a's, one of which, approximately 3 minutes after powering up, starts to oscillate and the vu meter starts rocking back and forth while the vu light is dimming simultaneously. This doesn't stop until I switch the unit off. Trouble is, it only does this in my studio. I've already sent it to an experienced tech twice and he could not reproduce this fault, even when leaving the unit switched on for hours at a time. He tried it in various places. Back at my studio, it happens every time I switch it on. Even when nothing is connected to it. I also tried all available power outlets in my house...
Could this be a power issue? I find it really strange, since this is the only unit playing up. The second La3a is fine and all my other outboard too. Whenever I take it out of my house, it seems to work just fine. (?)
Help and pointers appreciated.
Thanks for your time