A diode clamp is simply? a pair of REVERSE connected diodes, like 1N5408 / 6A10 / PM-600? type diodes.? ?They are wired between the B-? and the chassis.? Then the B- can never wander more than +/- .7 vdc? from chassis potential.
IF the? B+ anode ever arced to the (grounded) grid, the fault path is then through the chassis....and up out of the chassis, through one of the diodes...and back to B-? which completes the loop...and the HV fuse opens up asap, in < 1 msec.?
I use a 750 ma HV fuse in series with the B+ output ( instead of drakes .82 ohm resistor)....then a 50 ohm @ 50 watt wire wound resistor.? The 50 ohm resistor will? LIMIT the fault current to just 2500/50 ohms = 50 amps.? And 50 amps of fault current will OPEN OFF? a 750 ma rated? HV fuse in < 1 msec every time.?
Without the RVS connected diodes wired between? ?B- and chassis (I install em in both the L4PS / L7PS? HV supply....and also the RF deck) what happens is the fault current will flow into the chassis (anode to grid arc)...then up out of the chassis...then through the grid shunt,? grid meter pegs backwards.......then? through the plate current meter (plate current meter pegs forward)...then? back to the B-? of the HV supply, destroying both meters in the process.?
