----- Original Message -----
From: "Joe Loverti" <[email protected]>
To: <[email protected]>
Sent: Sunday, November 21, 2010 1:36 PM
Subject: [Drakelist] Sudden power loss on T-4XC... A Weird
Solution!
Hi guys:
Last week my son in St. Louis (WS8X) posted a question
about a sudden
transmit power loss on his newly purchased T-4XC. After
trying some of the
suggestions he received with no success, he brought it
home to me (WW8X) in
Miamisburg to take a look at before having a pro find the
problem.
I took the top of the RF cage off and noticed the cap on
one of the 6JB6s
was loose. I touched it and it broke clean away from the
tube! I also
noticed the resistor connections to the plate caps were
weak... so weak that
with a small jiggle, they both broke loose. I re-soldered
the plate cap back
to the small wire that was luckily still sticking out of
the tube and
re-soldered the plate cap resistors back in place. When we
turned the rig on
we got full RF power out on all bands!! I was luckily able
to repair it
without buying new finals. Problem solved.
I'm wondering how common is it for a plate cap to break
away from a 6JB6
like that? It seemed awfully weird for that to have
happened??
73,
Joe
WW8X
Miamisburg
Ohio
I don't know about the 6JB6 specifically but have had
many plate and grid caps come off glass tubes in the past.
The solder joints become crystalized with age and perhaps
heat and the cement used to hold the caps to the glass is
not very strong. Often you can just resolder the cap but
sometimes the lead from the tube breaks off and you are
cooked. I think all the solder joints around the plate cap
are subject to enough heat from the tubes to be affected
over a long period of time and, after all, these
transmitters are getting old.
--
Richard Knoppow
Los Angeles
WB6KBL
[email protected]
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