[Joeztech]

Madmurdok, about the runaway tubes in the Dynaco Stereo 70, I experienced the same thing with my Stereo 70 in the late 70s and eventually replaced it with a solid state Marantz DC120. In retrospect, although I originally blamed the problem on bad new tubes (grid leakage after warmup) I now know that there was an known problem with the quality of the tube sockets. Restorers now recommend replacing the output tube sockets with better quality sockets. The OEM sockets had a tendency for the grid contacts to spread easily and during warmup the contacts would fail to touch the grid pins of the tubes resulting in runaway conduction. I had some on my unit that got so hot the glass sucked in against the plate structure. That did not help the rectifier tube either. Of course the selenium in the bias circuit should be changed. I always hated the odor of failed selenium rectifiers.

Joe