Many years ago, when Lincoln was still president, i repaired and tried out a BC-474. It suffered “fringe howl”,

and to solve that, i connected a damping resistor across the output transformer primary. Now today i read C1

to TM 11-250, and it sez to “ground pin 1 of VT-148 socket to chassis, using shortest possible connection. This

will result in the tube shield being grounded through its clip…”

Now how did i miss that in 1985 ?

BTW, i don’t think i have ever read a completely convincing explanation of “fringe howl”. Someone on the old

Regenrx email group stated it was due to negative resistance in a regenerative stage, but it seems to me it has

something to do with capacitive feedback and the Q of an inductive output device.

-Hue Miller