Hi All!
I'm Dave, KW0D, and recently acquired a nice Omni VI / Centurion pair used
out of an estate. Love it already... I've been using it every night for
the last week.
Last night, I got quite a suprise. I was tuned up on 160m, rag-chewing with
friends, load was right on 1:1, and I wasn't transmitting. I had my face
buried in a bowl of chocolate ice-cream at the time... listening to the
other guys chat, when the Centurion let out a horrendus Ka-Rack! It
startled me so much that I dropped a spoonful down my shirt trying to get
the power shut down... meanwhile the other ends of the ragchew went on like
nothing happened.
I looked around the tube compartment with a flashlight and found nothing...
no dust bunnies, no burn marks on the HV circuits nothing suspicious, so I
hooked it to a variac and brought the HV up slow, all went just fine, all
the meters were responding fine. I brought the drive way down and
attempted a tune- had a little grid current, but no output... I brought up
the drive just a hair and watched Ig, it jumped up, but no output, so I
shut it down, waited a few minutes, then opened it for a look- that's when
I found the piece of sphaghetti tubing and stray HV wire.
This Centurion has been transported back and forth across the country twice
by non-hams, so it's been jiggled around a bit. It looks like the
sphaghetti tubing insulating the bottom end fatigued the wire right at the
choke, breaking it off and dropping it against the deck.
Unfortunately, the wire broke RIGHT AT the end of the plate choke... no
burn marks anywhere on the choke. As an experiment, I pulled the tube deck,
unwound one turn from the choke (just enough to reconnect to the HV stud)
scraped it clean, and soldered it back down, reassembled, and checked...
back to normal, but a little bit out-of-breath. I probably didn't get all
the enamel scraped off... but it showed no other signs of problems.
Just talked to Paul in parts about it, he says loosing one turn will change
the suck-out point, so I ordered another choke. I'll pull this one out,
modify it, and put it into service in another amplifier project
elsewhere... and put the new choke in the Centurion.
DK :-)
73's from KW0D Dave
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