10-06-2012, 03:39 PM
I doubt that the 10V drop in your B+ is your problem, but more of a symptom of your real problem. Something down the line is starting to draw more current once warmed up. I would start with some tube substitution, you may have a gassy tube. Just my thoughts. A tube testing probably wouldn't catch it.
Good luck and keep in touch.
Jerry
Good luck and keep in touch.
Jerry
A friend in need is a pest! Bill Slee ca 1970.