"Byron Tatum" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Hello Rich-
One thought comes to mind -- Are you sure the crystal itself is
oscillating and not the L/C circuit of adjusting coil? I believe in a
previous message I saw frequencies listed, which were measured ,and they
reasonably agreed with the crystal frequencies. But thought I would ask this
first before ruling it out.
Thanks, Byron WA5THJ.
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, January 22, 2008 2:03 PM
Subject: [drakelist] premizer alignment puzzler
[EMAIL PROTECTED] made an utterance to the drakelist gang
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I am in the process of restoring a TR-3. I've spent a great deal of time
trouble-shooting the premixer, but I'm stumped. I'm about ready to throw
my hands up and send it out for repair. I'm not too cheap to pay someone
to help out with this, but I started restoring this rig to help become
more familiar with tube transceivers and analog circuits. I hate to give
up.
The radio works well on 20 and 80 meters. On 40 meters, the premixer
oscillator runs at 16.3 mhz instead of 20.5mhz. I get no power out. On
the 15 and 10 meter bands, the crystals read low by about 100khz. Last
night, I poked around with a scope a little more and tweeked the 20m
crystal alignment inductor and suddenly the premixer was working. I had
precisely 20.5mhz on 40m and the other bands measured correctly too. I
found two leads under V3 that looked like they may have been shorted, so I
blamed my problems on that.
Emboldened with success, I proceeded to run through the alignment
procedure. I went through the injection coupler alignment and on to the
receiving IF alignment. Then everything went south again. Figuring that
maybe I had a thermal issue, I turned the rig off and let is sit
overnight. My hope was that this morning I would find the premixer
working again. No such luck. I suspect that there may be something wrong
with the alignment I did. I've double-and triple checked the steps in the
procedure. I've poked around with an insulated tool to see if I could
find a bad solder joint or cracked component. I've cleaned the band
switch several times.
The alignment instructions were written for folks who lacked modern test
equipment. Maybe there's an easier and more precise way to align the
premixer. If it isn't something I did, then there is something marginal
or intermittent in the circuitry.
I'll have to admit that my analog background is limited. I can use a
scope and I'm comfortable with digital circuits. I have a good scope and
know how to use it. I'd appreciate any pointers from the group. I know
that Mark (N1VQW) is wrestling with his premixer too, so any tips would
probably get double-duty.
Thanks in advance
Rich KE1EV
--
Rich Carter
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