[R-390] Calibrator Problems

[jgedde at optonline.net]

Thanks Larry!

 

That’s exactly what the problem was.  A broken wire to the relay coil.

 

John

 

From: Larry H <larry41gm at gmail.com> 
Sent: Saturday, May 4, 2019 4:14 PM
To: jgedde at optonline.net
Cc: R390 (E-mail) <r-390 at mailman.qth.net>
Subject: Re: [R-390] Calibrator Problems

 

John, The antenna relay should ground the antenna in the Cal position.  The cal signal should be about 10 to 20 db.  If the antenna is not grounded, the cal signal can be covered over.

 

Regards, Larry

 

On Sat, May 4, 2019 at 11:07 AM <jgedde at optonline.net <mailto:jgedde at optonline.net> > wrote:

I had my RF deck out yesterday to replace a few more bad resistors.  After I
put it all back together, I noted some strange behavior with the calibrator.
It used to be when I engaged the calibrator, it would swamp out anything
being received and I'd get clear calibration signals all over.  Now, they
seem feeble and are often overcome by stations being received or even noise.
With the antenna disconnected, I can hear them loud and clear.  

I'm a bit puzzled about the output from the calibrator's cathode follower.
I captured some oscilloscope waveforms which I've attached, and the
calibrator output is rather small compared to what's on the grid...  What do
you think?  The grid and the multivibrator were captured with a vertical
scale of 50V/div.  The output at pin 8 was captured at 500 mV/division.
Small in comparison.  I can't help to think it should be bigger sincew it's
coupled through a 1 pF cap into the RF amp.

John
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