Date: Sun, 6 Oct 2013 10:53:36 -0400
From: "Carl" <km1h@jeremy.mv.com>
To: "Pete Smith N4ZR" <n4zr@contesting.com>, <amps@contesting.com>
Subject: Re: [Amps] high voltage fuses
### say what ? If you want any HV fuse to blow asap, fuse it for no more
than 5-10%
higher than the amps steady state, key down current. Just make sure to put the
HV fuse BEFORE the
glitch resistor. The glitch resistor can go in the RF deck, or in the HV
supply. IMO, for max safety,
put it in the HV supply, or as close as you can to the B+ of the filter cap.
## A small ga wire, suspended between stand offs works just fine for a HV
fuse, with the provisio
that you 1st slide some heat shrink over the wire, use anything as long as it
barely slides over the
fusing wire. You don’t apply heat and shrink it to the wire either, just slide
it over. Or use some
88/33 tape, etc, and wrap the wire. Then when it blows open, you don’t get any
vapor deposits.
Those glass BUSS HV fuses can be refurbished too, Take the end off, and pour
out the sand.
Remove other end, clean it up and solder in a new fuse wire, and pour the sand
back in.
Re-assemble the mess.
## The 5 kv, .75 – 1.0 amp microwave oven HV fuses work just fine.
I also install a 2nd HV fuse, between one leg of the plate xfmr sec and the
FWD... or FWB.. Either leg, only one fuse required.
## Drake used a .82 ohm @ 1/2 watt CC resistor for a HV fuse in the B+ line.
That works too, and blow cleanly in half.
later... Jim VE7RF
Thats a bit too close for even a 1200W amp. Might be fine for something in
the SB-200/AL-80 size amp.
Size the fuse at 2 to 2.5 times the actual peak current, not steady state
key down.
Carl
KM1H
----- Original Message -----
From: "Pete Smith N4ZR" <n4zr@contesting.com>
To: <amps@contesting.com>
Sent: Sunday, October 06, 2013 10:30 AM
Subject: [Amps] high voltage fuses
> For what it's worth, I see that there are a lot of inexpensive 5KV
> 0.75-1.0 amp glass fuses listed on ebay for microwave oven use. I assume
> these would also work in a legal ham amp?
>
> --
> 73, Pete N4ZR
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