My guess is the bias supply caps are probably bad and you are getting AC on
the bias which does not show up on the meter. (The peak AC volts are
masking your DC set point). At least replace the bias electrolytics, but
why not just put in an AC-4R board with all new parts including all the
electrolytics.
Lee, w0vt
----- Original Message -----
From: "Bob Fish" <[email protected]>
To: <[email protected]>
Sent: Thursday, May 07, 2009 2:02 PM
Subject: [Drakelist] T-4XC Problem
Hi Guys,
My T-4XC has stopped transmitting. I have normal idle current. But not
much more. If I turn the gain way up I can get a barely perceptible dip in
plate current.90 or 100 ma. So I turned the bias voltage all the way down
and put it in tune very briefly to see if the finals were at least
functional. I get about 260ma when I do that. I presume this means they
still work?
It looks like I have lost drive somewhere. I checked the carrier
oscillator and it is up and running, I can see it with a scope and a freq
counter. However, I don't see my 5.645 Mhz at the plate of V2 (IF amp). I
did a voltage check and all of the voltages on V2 look normal. Then I did
a resistance check on V2. I found everything normal except the cathode
measures 5.5k to ground. The book says it should measure infinite. Is this
potentially my problem or is this non critical. I thought I would see if
you guys think I am on the right track before I start lifting one leg of
every cap in that circuit.
Thanks,
Bob K6GGO
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