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Ten-Tec 580 Digital Dial Difficulty ...

To: <tentec@contesting.com>
Subject: Ten-Tec 580 Digital Dial Difficulty ...
From: rjenkins@pcug.org.au (Richard Jenkins) (Richard Jenkins)
Date: Tue, 09 Apr 1996 21:39:58
Greetings fellow interested Ten-Tec type person...

I have owned a model #580 for more than 11 years now and have used
it for SSB and AMTOR/RTTY operation.  Over the time I have used it
the only failures were a couple of dial lights and a LSB crystal.

Last weekend I changed antennas to a 102 ft flat top - which I
feed with 300 ohm ribbon cable.  This works well, but I had to
transmit short bursts of carrier while I tuned up the antenna. 
You know the routine - switch to CW, and pull out the ALC control
switch while adjusting the mic gain until you get enough carrier
to get a reading on the SWR meter.

Well, I got some settings which worked fine on 40.  Then I reset
the controls and I noticed that I had lost the digital display. 
Now when I turn the set on the dial reads about 3.5MHz high (and
this reading is not changed by dial position).  After it warms up
I get a cycling display which is about right but cycles over and
over across a range of frequencies... and never slows down/ or
stops. The set is working normally (ie it receives and transmits
okay) ... it's just the display dancing all over the place that is
so damn distracting! 

I figure the problem is on the pcb with the display circuitry. 
The randomness of the problem seems to suggest that either I have
"cooked" the dual gate FET mixer ... which blends the VFO
frequency and the BFO, or maybe I have got a dodgey xtal.  Any
thoughts on the probable cause of this "problem" would be
appreciated as I want to put the old beast back on air as soon as

Thanks heaps

de Richard

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