[Amps] Crowbar that HV!

[Mark Hill]

Folks,

Talking of protection.  I'm contemplating building an crowbar for the 
HV supply in my 3CX3000A7 PA.

The PSU filter capacitor is really too large (130 uF) and the amount 
of energy it holds when charged to 5 kV is frankly scary.  Eimac's 
AB17 seems unclear about how much of a bang this valve can take (4J; 
50J; something in-between?).  I'm not sure whether my ear drums would 
be OK under conditions of flash over either!

I found an interesting article here:
http://www.astec.ac.uk/rf/rf_preprints.htm (a little way down the 
page there is a PDF file entitled, 'A Solid State Crowbar for RF Tube 
Protection').

I like the way that the series thyristor combination appears to have 
been driven, i.e. individual current transformer for each device with 
a common primary turn through them all.  Has anyone tried this 
technique?  Seems as if it might be cheaper and potentially more 
reliable than a bunch of opto couplers and transistors etc.  Is 
anyone on the line using a crowbar of any description?

Regards.

Mark.
*******************************************
Mark Hill - G4FPH
E-mail: g4fph at mjha.co.uk
Current web pages at: www.g4fph.net
Old web pages at: www.qsl.net/g4fph
----------------------------------------------------------------------
Dipoles resonant on 1942 / 3720 / 7085 kHz
Three element wire beam coming soon on 14180 kHz!
----------------------------------------------------------------------
Remember - SIDE for HV safety:
S witch off
I solate
D ump
E arth
*******************************************