Carl wrote:
> Of course you could always employ the method detailed by John Lyles about
> instantaneously (almost) dumping the capacitor bank in a 500KW amp!
>
Get someone to stand next to it, that has never had the honor of seeing
how fast a crowbar can work.<:-))
Of course the Varistor route is also spectacular when dumping 50,000
joules off a 480 primary that had the switching get out of sequence
under load. Nothing left but the backing plate and two #6 wires standing
straight out. If the supplies on either side of you were working, you
always made sure they were not about to do any switching while you were
in there. Those transformers were taller than I am and I've forgotten
how many tones they weighed. When using smaller rated GMOVs they need
to be contained in a compartment or in some manner to keep the pieces
contained.
73
Roger (K8RI)
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Dave white" <mausoptik@btinternet.com>
> To: "Alex Eban" <alexeban@gmail.com>; "'Angel Vilaseca'"
> <avilaseca@bluewin.ch>; <amps@contesting.com>
> Sent: Wednesday, July 22, 2009 10:15 AM
> Subject: Re: [Amps] inexpensive HV fuse
>
>
>
>> 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@gmail.com>
>> Sent: 22 July 2009 12:14
>> To: 'Angel Vilaseca' <avilaseca@bluewin.ch>; amps@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@contesting.com [mailto:amps-bounces@contesting.com] On
>> Behalf Of Angel Vilaseca
>> Sent: Wednesday, July 22, 2009 9:21 AM
>> To: amps@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
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>>
>
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