On Tue, 21 Apr 1998 14:47:54 -0400 "Kenneth D. Grimm"
<grimm@lynchburg.net> writes:
>Usually a lurker, I can't help but jump in here with an "amen" to your
>comments about arcs vs. parasitics. The big "bangs" in my experience
>had to do with blocking caps letting go, HV connectors breaking down,
>etc. My first and really most frustrating effort at amp building was
>4
>811As. I had managed to collect 16 of the bottles and thought I had a
>lifetime supply. I foolishly watched while the plates turned white
>hot
>and melted in a matter of a few seconds with no noise and no drive.
>What was this demon that was destroying my tubes? After sacrificing
>all
>16 on the alter of the demon parasitic, I gave up on 811s and moved on
>to 813s. No problems there with parasitics, but there were a few
>bangs
>before I got the right components in place. I'm not saying that
>parasitic activity can't be accomponied by sound and fury, just that
>in
>my experience it was a silent killer.
Well Ken, I just had that experience yesterday. Put a new set of Svetlana
572B's in a otherwise fine SB-200 and watched them light up and go white.
Must be a bad case of internal gas since after the fact the tubes had a
fine coat of gettering material. Put in a new set of Chinese and the amp
is running a stable 800W.
73 Carl KM1H
>
>Ken K4XL
>
>km1h@juno.com wrote:
><a bunch of stuff snipped>
>> Even an out of control parasitic will not cause a bang initially.
>The
>> tube will run away, the plate current will soar and the tube may
>fail but
>> this takes several seconds from start to finish and is usually a
>silent
>> process in the vacuum of the tube. The bang in this case is usually
>a PS
>> path failure.
>>
>> 73 Carl KM1H
>
>--
>Ken K4XL
>grimm@lynchburg.net
>Boatanchor Manual Archive - ftp://198.28.36.115/pub
>
>
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