On 4/15/2011 8:27 PM, Kenneth Scharf wrote:

If there IS an rf bypass capacitor between the 'cold' end of the plate
choke and ground then my suggestion isn't needed. If the only bypass at
the cold end of the choke is though the power supply, then one should be
added. In some amplifiers a second rf choke is placed in series with the
main plate choke and a bypass capacitor to ground is placed between
them. Such a bypass capacitor should be one of those 'doorknob' types.

Thanks, Ken, good points.

Basically the added 10 Ohm 10 Watt resistor
is intended to interrupt the energy from the power supply
electrolytics in the event of an arc-over in the final tube.
By the time the primary fuse kicked in, the damage would be done.

They do sell HV fuses suitable for the purpose, used
in microwave ovens. I see some on eBay for around $8 each,
rated for 5KV interruption.

73,
Ed Knobloch