John T. M. Lyles wrote:
>For HV "glitch" resistor, avoid wirewound construction, both in the
>sand packages or in the big tubular ceramics, for 5 kV 1 Amp and higher
>supplies. Carborundum is the best way to go, if you can get them from
>Kanthal Globar or whoever they are called now. You can find them
>surplus sometimes, check around Fair radio and others.
>
>Inductive wirewounds are basically an air solenoid, and if you force a
>lot of current through it, the winding will collapse due to EMF. Also,
>they sometime will just track over the length in a burst of flame with
>too much HV.
>
I've "seen" both of those, when providing remote diagnostics for people
using my Triode Board without an effective surge resistor. In one VHF
amp, the air-wound RF choke was completely crunched up by the magnetic
field created by the surge. In a YC1556 amp, the glitch resistor wasn't
long enough for the very high voltage, and had tracked from end to end
(but no flames in that particular case).
>If you can use a string of resistors might get by with carbon types.
Has anyone tried a typical dummy load resistor (usually carbon film on
ceramic)? The long, thin shape is right... here in England we call them
"cricket stumps".
Happy Holidays, all!
(CU in a few days)
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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