----- Original Message -----
From: "Eddy Swynar" <deswy...@xplornet.ca>
To: "Curt" <cptc...@flash.net>
Cc: <drakelist@zerobeat.net>
Sent: Thursday, December 22, 2011 10:08 AM
Subject: Re: [Drakelist] Speaking of breaking Glass...
On 2011-12-22, at 12:54 PM, Curt wrote:
All looks ok EXCEPT..the one tube that was bright has a
small suck-hole thru the side of it. It got so hot, the
glass melted and a hole was sucked thru the side without
breaking the rest of the tube. YIKES>
Hi Curt,
That happened to me one time here, too, only the
circumstances were a bit different...
I had a brand new pair of 811A tubes in my 500-watt
amplifier, & had just purchased a Yaesu FT-980. I got so
enamoured with my being able to "...raise the average talk
power" of my SSB signal by virtue of the new rig's speech
processor that after about 5, or so, DX QSOs on 20-meters,
the fuse in the amp's power supply popped. I replaced it
with a new one, and again, it blew...
So I took off the amplifier's covert & examined the new
tubes...and lo & behold, there was a tiny pin hole in the
envelope of one. I guess my speech processor raised the
plate dissipation of those jugs as well as my "...average
talk power", to the point that the one tube got so hot the
glass had softened, & the vacuum was sucked out!
I've never used a speech processor since that time.
~73~ de Eddy VE3CUI - VE3XZ
Eimac featured this effect when they began selling
ceramic tubes. They showed a picture of a glass tube with a
suck-hole in the side and a ceramic operated under the same
conditions that did not. I think they said the suck hole was
the result of electron bombardment of the tube at high
frequencies but its possible that any inclusion or weak spot
in the glass could do it. I've had tubes crack from
overheating but have never had a suck-out.
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
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