I believe the answer may be found in the geometry of the tube being used.
About 40 years ago I built a beautiful (for that time) amp using pp 4-400A's
4" 13x17x4 Aluminum chassis, air system sockets,chimneys, big Johnson jack
bar with kw coils,swinging link ,3 nice big Triplett meters, all in a black
crackle desk top rack. Sure worked fine, only had one trouble, XYL couldn't
turn off the bathroom light when I was on 75M. The screen supply was not
regulated seems like the big old glass fire bottles didn't need it. But the
external anode tetrodes Eimac, Svetlana and others, do need regulation in
conventional circuitry, About the G2DAF I have no opinion and am waiting to
get comments. I have never seen the Ig2 on a 4-400A go negative but it is
common on the 4Xand CX250B, different screen geometry no doubt.
Bob,w5pvr
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