[AMRadio] Fuse advice


kenw2dtc kenw2dtc at comcast.net
Wed May 28 12:52:12 EDT 2008


Bob,

I've had two shorts in the many years of using this type of fuse.  The wire 
disentegrates, there is no trace of the wire after opening.  Note that the 
fuse is on standoff insulators also.  The subject of this fuse type was 
limited to tube amplifiers.  I made the length 4 inches so any possible arc 
could not continue at that length with voltages of 5000 or less and the 
standoff insulators would be too far off ground to allow for an arc.

I would not use the wire fuse on delicate equipment, but for amplifiers, it 
has worked fine for me, for years.

73,
Ken W2DTC

__________________________
Ken Barber  Middletown, NJ
Website: http://w2dtc.com
__________________________


----- Original Message ----- 
From: "rbethman" <rbethman at comcast.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Cc: "Rick" <rickb at tx.rr.com>; "kenw2dtc" <kenw2dtc at comcast.net>
Sent: Wednesday, May 28, 2008 12:37 PM
Subject: Re: [AMRadio] Fuse advice


> Ken,
>
> I have to speak up AND out *AGAINST* this methodology!
>
> A 4" piece of wire that parts somewhere in its length MAY very well 
> DEVELOP an arc to some point of ground!
>
> I saw just this happen when a fuse failed on a piece of equipment.  My 
> supervisor, being an EE, decided to replace the fuse element with 
> "supposedly" an appropriate gauge wire in the fuse body.
>
> A WHOLE lot of damaged was done to the equipment, and people were 
> needlessly put in danger.
>
> Rick,
>
> The value, coupled with the physical size of this fuse, tells me it HAS to 
> be available.  The reason being is that it is one that would "normally" be 
> used in power generation for instrumentation either in a PT, (Potential 
> Transformer for voltmeter), or CT, (current transformer for ammeter).
>
> HV fuses - 2.5 KV and up - that are encapsulated in an insulated closed 
> housing "usually" have a compound similar to sand.  This is used to quench 
> the arc that develops when the fuse "link" opens.
>
> Bob - N0DGN
>
> kenw2dtc wrote:
>> "As much as I'd love to keep this original I see I will have to use 
>> something else here.  Any ideas?"
>>
>> Rick,
>>
>> I use magnet wire for short circuit protection.  Check photo #8:
>>
>> http://w2dtc.com/w2dtc-hv-power-supply-page.htm
>>
>> 73,
>> Ken W2DTC
>> 



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