I would bet you have a pin not making good contact.Go to your local auto supply and purchase a spray can of electric contact cleaner.Spray your tube pins and sockets.Should take care of your problem. Mike
Tube glows cherry red...then it doesn't ?
The other morning I warmed up my power amp and sat back with a cup of coffee to listen. A couple minutes later I got up and on the way out of the room noticed that one of the eight GE 6550A power tubes was glowing cherry red. I immediately turned down the bias and check the other tubes. They were all normal.
Over the course of the next twenty minutes the current drifted downwards and I kept rebiasing to keep the current constant at the nominal value. The setting of the bias control went back pretty much to where it had been before this mysterious event occurred.
For the past few days since it has behaved normally.
What gives?
Over the course of the next twenty minutes the current drifted downwards and I kept rebiasing to keep the current constant at the nominal value. The setting of the bias control went back pretty much to where it had been before this mysterious event occurred.
For the past few days since it has behaved normally.
What gives?