[Elecraft] new owner looking for fuses.

[K9MA]

Also, fuses rated 250 V AC are typically rated only 32 V DC.  That's 
because, with AC, the current goes to zero twice per cycle, so the arc 
can go out. Not so with DC. I suspect the standard 28 V DC once used in 
many aircraft was chosen because that's about the highest voltage which 
can be switched with a mechanical relay or switch. (Something about the 
energy required to strip electrons from the metal contacts.) Solid-state 
switches, of course, don't have that problem, hence the popularity of 
higher voltage DC systems now.

Long ago, I put a 3AG fuse in series with the finals' cathodes of a 
T-4XB. The first step in replacing that fuse when it blew was to shake 
all the glass out of the radio.

73,
Scott K9MA



On 7/15/2018 05:22, Roy Koeppe wrote:
> One reason 'all fuses' aren't just rated at 250v to be done with it is 
> that a shorter element section in a lower voltage fuse can have a 
> lower resistance, due to the shorter arc gap allowed. Thus lower 
> voltage drop for a low voltage circuit, etc.
>
> 73,   Roy    K6XK
>
>
>
>
>
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-- 
Scott  K9MA

k9ma at sdellington.us