[Boatanchors] HV fusing in amplifiers
Mike McCarthy, W1NR
lists at w1nr.net
Wed May 4 21:04:47 EDT 2005
I don't agree that it will "arc all over" given sufficient clearance around
the element. The sand in the fuse is also to douse the molten metal and
keep what's left from coming into contact with surrounding components. Yes,
there will be some molten metal sprayed around when the wire does go.
The 30ga wire method is documented in several amplifier construction
articles.
-----Original Message-----
From: Rbethman [mailto:rbethman at comcast.net]
Sent: Wednesday, May 04, 2005 10:43 PM
To: Mike McCarthy, W1NR
Cc: Boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] HV fusing in amplifiers
The wire between ceramic standoffs is a DANGER. There is NO quenching
action for the arc when the element blows. HV arcs MUST be contained to
keep them from arcing all over. Design of HV fuses usally has either sand
or some powder internal to the cartridge to kill the arc.
Bob N0DGN
Mike McCarthy, W1NR wrote:
>Bussman type HV fuses are made just for that purpose. I have an old
>Henry 2K that uses an HVB-2 in the high voltage line. When it blew, I
>soldered a piece of #30 wire wrap wire across it. I have not found any
>place to buy just one, only by the box of 40. HVB's are rated for
>2500V. I have a box of HVJ-2's which are rated for 5000V at 2A but are much
larger in diameter.
>Bought them at a flea market. See
>http://www.bussmann.com/library/bifs/6003.PDF for specs. Mounting is
>via metal clips attached to ceramic standoff insulators.
>
>For real cheap, a 3" piece of #30 suspended between ceramic standoffs
>would work just fine.
>
>Mike, W1NR
>
>-----Original Message-----
>From: boatanchors-bounces at mailman.qth.net
>[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Rbethman
>Sent: Wednesday, May 04, 2005 7:59 PM
>To: Boatanchors at mailman.qth.net
>Subject: [Boatanchors] HV fusing in amplifiers
>
>Group,
>
>Has anyone thought about high voltage fusing in an amplifier or "old" BA?
>
>Usually there is a choke in the RF output leg to ground, in the event
>that the plate blocking cap fails.
>
>Yes, we usually have power supply fuses or circuit breakers. BUT -
>what will get fried? How do you protect all that?
>
>I've got ONE HV fuse by GE. Its design voltage is 2400V. It is rated
>at 7A, which is obviously a ridiculous value. HOWEVER, even IF it was
>a reasonable current rating, it is HUGE! It is 11" long and 2" in dia.
>
>Where in the world would you even mount it?
>--
>Bob - NØDGN
> Bob Bethman - NØDGN
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--
Bob - NØDGN
Bob Bethman - NØDGN
\\"""// \\"""//
(@ @) (@ @)
+-------oOOo-(_)-oOOo--------------------------oOOo-(_)-oOOo-------+
| NØDGN AMRadio Manassas, VA | REAL Tube Radio and AM |
+-------------------------------+----------------------------------+
| Manassas Radio - Home of Homemade Kielbasa & Pirogi |
+-------------------------------+----------------------------------+
| Bob Bethman \\\|/// " The absence of a danger |
| rbethman(at)comcast.net \\ ~ ~ // signal does *NOT* mean |
| (/ @ @ /) that everything is OK " |
+-------------------------oOOo-(_)-oOOo----------------------------+
| <http://home.comcast.net/~rbethman> |
| 1 BC-61ØI w/BC-614I,1 T-213/GRC-26 w/BC614I 1 '51 Collins R-390A |
| SP-600/NR Type 159, Heath DX-60, Apache, Mohawk, SX-101, HT-32A |
+-------.oooO---Oooo.---------------------------.oooO---Oooo.------+
| ( ) ( ) ( ) ( ) |
| \ ( ) / \ ( ) / |
| \ _) ( _/ \ _) ( _/ |
+------------------------------------------------------------------+
| Amateur Astronomer - Celestron Nexstar 8 |
| 12" f5 Dob coming soon! Being built |
| Meade ETX-6Ø |
| 38 Deg 46'48.62"' N - 77 Deg 28'26.89" W |
+------------------------------------------------------------------+
| Opinions expressed are that of my own and do not necessarily |
| coincide with or represent those of ANYONE else |
+--------------------------.oooO---Oooo.-------------------------+
( ) ( )
\ ( ) /
\ _) ( _/
|ALL E-mail received and sent scanned by AVG & Norton System Works |
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