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[AMPS] tube structure/failure.

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Subject: [AMPS] tube structure/failure.
From: (KL7RA Fairbanks Alaska)
Date: Wed, 07 May 97 17:28:46 utc
Skip's story leads me to report a similar story with different

I was trouble-shooting a parasitic in a new homebrew 3-500z's amp.
When the tune control was moved the plate current shot up, the p/s
screamed and the tubes went from red to pink in a second or two.
This to me is an indication of a parasitic. 

I did the normal things, add/subtract windings on the suppressor,
redid the grounds on the tube sockets and repositioned the
plate/load caps, etc. Surprisingly after multiple attemps at repair
I never lost a tube. I assume here had I left the B+ on the tube
any longer then I did, it would have eventually failed due to
catastrophic element failure of some sort. I leave it to this forum
to decide which element. 

After reaching into my bag of 2 watt 50 ohm carbon resistors to
wind z1/2 number five I stopped and examined my Dayton flea market
specials. Opened one up, no carbon. Wirewound. They looked like
carbon. Made like carbon. Bag was marked "Carbon". 

The bag is on the shelf next to my Dayton flea market 13 volt
zener's that are really 12 volt and my 500/1000pf dc leaking super
good deal door-knob caps, the "I can't believe they are only 250
dollar 8877's" and the 85$ rotor control box I bought from a "60
years in ham radio" oldtimer that was taken off his operating desk
just that very morning. Obviously after the lightning hit as no
parts were left on the meter board.

See you at Dayton. I'm usually in the flea market dealing with
people with names like Fleamarket Fred for a "brand new" 4-1000.

Rich KL7RA 

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