[mikethedruid]

Selenium rectifiers are either good or bad. If it works, it works. They usually have fins on them for air circulation cooling. I have never seen one in a tube, can't imagine it, unless that tube had a fan with it to direct an air flow over the selenium rectifier. Pictures of this set up might help. Oh, and, in case you don't have a manual, I found one free on the net : https://elektrotanya.com/telefunken_opus...nload.html