[AMRadio] hamfest tubes


Jim candela jcandela at prodigy.net
Tue Aug 17 23:50:52 EDT 2004


Steve,

	Once upon a time I built a 16 transistor audio driver for a pair of 811's
in my Globe King 500. The final 8 transistors were all direct coupled (4 for
each 811) and driving the 811 grids directly. I had a lot of test equipment
at my disposal, and I was working in a R&D laboratory. That driver could put
+100 volts peak at something approaching 1 ampere on those 811 grids for a
little while. I did this on the bench with no plate voltage as a test. A
true nearly zero source impedance driver.

	Anyway I used this rig for several years until I bought a half dozen or so
used 811's at a swapfest (Manchaca). Well one of those 811's had the grid
touching the plate... I tried the 811's one at a time until that one was put
in. Remember the sci-fi show "voyage to the bottom of the sea" where the
electronic panels would emit sparks, smoke, and noise like the fourth of
July whenever the Seaview submarine was under attack? Well when I hit the
plate switch that is exactly what happened, and the damn plate relay
contacts welded until the fuse blew. Needless to say I learned a valuable
lesson, and all 16 transistors were now fused silicon. Sigh.

	I never did rebuild that driver....I replaced it with a pair of 6B4's in
AB1 P-P.

Regards,
Jim Candela
WD5JKO


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of SBJohnston at aol.com
Sent: Tuesday, August 17, 2004 8:56 PM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] hamfest tubes



My worst deal on tubes at a hamfest was a bunch of 6HF5s I bought "new in
the
box"...  trouble was, half the boxes were empty!

Steve WD8DAS

sbjohnston at aol.com
http://www.qsl.net/wd8das
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