[Amps] inexpensive HV fuse

[Dave white]

I concur.....

If you want to limit flashover damage use a high power surge limit resistor in the HT line between capacitor stack and plate choke, and use a fuse or overcurrent trip in the primary

There was a circuit in Dubus by OE5JFL which used optoisolators and other clever ideas to detect overcurrent and crowbar the ht away.  It seems a bit overengineered to me but I've seen it work well.

Like others are saying, fuses are too slow and you have no real idea of how a spring will behave.  Remember how much the tube costs and spend a few pennies on a surge resistor

Cheers
Dave G0OIL

-----Original Message-----
From: Alex Eban <alexeban at gmail.com>
Sent: 22 July 2009 12:14
To: 'Angel Vilaseca' <avilaseca at bluewin.ch>; amps at contesting.com
Subject: Re: [Amps] inexpensive HV fuse

Response time, guys!!!
Any thermally operated fuse is TOO SLOW to protect the tube.
Besides, the spring can carry many tens of Amperes before it heats up enough
to melt.
You'll probably blow up diodes and tube and God only knows what else!
Alex	4Z5KS

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Angel Vilaseca
Sent: Wednesday, July 22, 2009 9:21 AM
To: amps at contesting.com
Subject: [Amps] inexpensive HV fuse

Commercially available HV fuses are quite expensive.

I thought of using a small spring instead, like the ones in ball-point pens