On Wed, 10 Dec 1997 22:07:03 -0700 "richard w. ehrhorn" <w4eto@rmii.com>
writes:
>On Wednesday Dec 10 1997 km1h wrote:
>.
>
>>Which brings up another interesting question....Why doesnt the plate
>>choke open up during these Big Bangs? A #28 wire should not survive
>if
>>the reasons we keep hearing are true. Food for thought.
>
>Before we learned the hard way (it wasn't in the 3CX1000A
>data sheet in 1970) about the need for "glitch" resistors to
>limit fault current, tube arcs usually DID **EXPLODE** the
>#28 wire in the B&W 800 rf anode chokes we were using.
Was it an actual arc or another cause Dick? I've destroyed a few old B&W
800's years ago myself in one and two hole 4-1000A amps but thought it
was a particularly robust parasitic that those tubes are known for.
I remember one builder who even blew TV doorknobs used as plate choke
bypasses in 2x 4x1 amps. Blew right apart and wiped out the chimneys!
Eimac appeared to bring the current limiting issue up very late in the
game. RCA has had it in spec sheets for as long as I can remember. The
NCL-2000 of 1963 had a limiting resistor.
>I distinctly remember a couple hundred half-turns of wire
>scattered throughout the rf section - figured it must be the
>magnetic field created that blew the thing into nice symmetrical
>pieces of basically UNBURNED wire.
Same end results here but I'm sure not in your quantity!
BTW, do you still have any 3CX1000A7 sockets? I use that tube in my 2M
amp and have several spares but no sockets and have wanted to build a
222MHz version.
73 Carl KM1H
>73, DIck W0ID
>
>
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