[Amps] HV Wires, back-to-back diodes, and B- Wiring

[Jim Garland]

> With all this talk about B- diodes etc., I wonder what the recommended
> safety practice would be for an amp/supply arrangement where B- is not
near
> ground potential; for example, a grounded-screen tetrode amplifier where
B-
> is several hundred volts below chassis ground.
> 
> 
> Scott Townley NX7U
> Gilbert, AZ  DM43di
> mailto:nx7u at cox.net
> http://members.cox.net/nx7u
> 
I think that's a very interesting question, Scott, and I'm looking forward
to hearing other folks' opinions.  I don't see any obvious way to protect
such a circuit, other than fusing the HV line with, e.g., a safety resistor
that will explode in the event of a flashover.

The problem I see with grounding the screen grid, so that the cathode is
several hundred volts below ground potential (as is done with, e.g., the
Collins 30S-1), is that a flashover will basically dump the full B+ on the
screen, risking immediate destruction of the tube as well as the screen
power supply components. 

73,
Jim W8ZR