euro21:
"You wrote that filament tied to B+ (BTW why not to cathode?)."
B+ comes from the cathodes.
"You wrote that filament tied to B+ (BTW why not to cathode?)."
B+ comes from the cathodes.
You just saved me a bunch of work.
I moved the connection from B+ to the cathode (i.e. from one side of the choke to the other), and the noise completely vanished. Even with the crappy Selectron tubes. My assumption, like @Miniwatt, was that B+ and the cathode were at the same voltage, but I suppose there must be more than 100V of ripple at that node and that Vhk(max) rating was indeed being violated. Thank goodness tubes are more robust than sand.
Thanks everyone for the help!
