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[AMPS] SB-220 Glitch Resistor ???

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Subject: [AMPS] SB-220 Glitch Resistor ???
From: Ian White, G3SEK" <g3sek@ifwtech.com (Ian White, G3SEK)
Date: Wed, 29 Nov 2000 07:20:21 +0000
measures wrote:
>
>>
>>>>Something often overlooked is that even if you fit a glitch resistor to
>>>>handle current surges, there also needs to be some way of interrupting
>>>>the power input from the mains. I've heard of situations where someone
>>>>dutifully added a glitch resistor, but when the B+ was shorted the power
>>>>supply kept right on going because the fuse/breaker ratings were set too
>>>>high.
>>>
>>>Not sound advice.  The Heath HV supply is not capable of generating 40A 
>>>@3000v.
>>
>>Nobody but you imagined it was. 
>>
>>But *some* HV power supplies with high-rated mains fuses will keep going
>>for long enough to burn out the glitch resistor...
>
>selecting a glitch R that can be burnt out by a dead short is Not good 
>engineering practice.  
>
I agree with you that it's bad practice to use a small glitch resistor
instead of an HV fuse.

In the case I'm thinking of, the glitch resistor was sensibly rated for
power dissipation in normal operation. The bad engineering practice was
to use fuse ratings so high that they blew the glitch resistor instead
of the fuse.



>> and then the HV pops
>>up again.
>> 
>Mr. White --  How can the HV "pop up" if the burned out glitch resistor 
>is in Series with the HV supply, ? 

The mains transformer is still running because that over-rated fuse
never blew. The HV is still there on the smoothing capacitors.

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.com/g3sek

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