Hi again,
The small schematics and all the switching sure does makes circuit tracing
a challenge...
I was also thinking along the same diagnostic lines, but hoping for a "I
had the same problem and C110 was leaky" thing. ;)
Already been through the switches, tube pins, variable caps, alignment,
etc as normal routine. My gut says it's a cap.
I will investigate further when I have a chance. It's a nice rig and
bench time is always good time.
Thanks for your interest and 73!
Bill V.
-----Original Message-----
From: Richard Knoppow
Sent: Saturday, October 19, 2013 7:44 PM
To: Bill V ; drakelist@zerobeat.net
Subject: Re: [Drakelist] TR-4 AM Mode Receive Distortion...
----- Original Message -----
From: "Bill V" <wviga...@cox.net>
To: "Richard Knoppow" <1oldle...@ix.netcom.com>;
<drakelist@zerobeat.net>
Sent: Saturday, October 19, 2013 11:22 AM
Subject: Re: [Drakelist] TR-4 AM Mode Receive Distortion...
Hi Richard,
Your facts are undistorted... and I do have a scope.
Thanks and 73!
Bill V.
I have not had to deal with this problem in my TR-4 but
the fact that it affects only AM is a good clue for
isolating it. It eliminates the AF amplifier and leaves
pretty much the detector circuit. The detector is also the
first audio stage so the tube is suspect. I find it
difficult to trace circuits in Drake schematics (and others
too). I find it helpful to have a couple of large scale
prints made of the schematics and trace out the circuits of
interest with colored pencil or highlighters. That way you
can see what is going on at the switches. Drake mostly used
good quality plastic film caps so they are not so often the
cause of trouble but even plastic and ceramic caps can go
bad. I would also do the usual voodoo for older equipment,
namely to work all the screws that may carry ground and very
thoroughly clean the switch contacts. Its surprising how
much trouble these two things can cure. Also clean the tube
pins and sockets. May not help with this but poor contact at
tube pins is responsible for a lot of mysterious problems.
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
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