[Amps] HV fuse

[Joe Subich, K4IK]

The US broadcast television transmitters using "inductive 
output tubes" (IOT) - essentially a single cavity output 
with a gridded electron gun - used triggered spark gaps to 
discharge the beam (anode) supply.  It's been a while but 
I seem to remember 40 KV anode supplies with 1.0 - 1.5 Amp 
average anode current ... probably around 4 Amps peak. 
If I recall correctly, the power supplies had three phase 
bridge rectifiers and capacitor input filters with about 
10 uF of capacitance.   

The triggered gaps were made by EEG among others.  I saw 
the aluminum foil of #20 wire test a couple of times --- 
wrap a piece of bare #20 around the end of the "dead man
stick" leaving a 5 cm piece sticking off the end and 
reach into a live HV cabinet.  Worked like a charm (just 
be very certain you touched AFTER the sense resistor - 
a current transformer in one case).   

> Bottom line: if you're going to copy OE5JFL's circuit, 
> copy *all* of it.
> 
> http://www.qsl.net/oe5jfl/flashover.htm
> 

I would be concerned about timing issues in a design that 
uses a cascade of devices to withstand the higher voltages. 
If they don't all trigger at exactly the same time there 
is a real chance of a cascade failure. 

73, 

   ... Joe, K4IK