HR-1680

[Stu Lyon]

Hi Fred,
I think the LSB  crystal is off frequency. I no longer have a HR-1680 or its
schematic but I remember it as having the same IF and conversion scheme as
the SB series. If the LSB crystal were too far down on the filter passband,
the lows would be filtered out -- just the effect you are experiencing.
Another possibility is that the crystal filter may have the wrong or bad
crystal installed. However, this should effect the USB/CW response in some
way.

When I did have a HW-1680, I was able to increase the sensitivity by
properly tuning the front end. The low range trimmer caps are inadequate to
properly tune to the operating frequency.  What I did was to set the trimmer
capacitors mid-range, remove the fixed padders then tack a larger variable
capacitor (like an APC) where the fixed padder was installed. The circuit is
then peaked with the larger variable. Measure the variable (I used a
Q-meter) and replace it with the closest dipped mica padder. As I recall,
this required many plugging and unplugging in the of the board which sure
cleaned the contacts.  And a good selection of mica capacitors.

Good luck es
73, Stu W6CUX
Winnetka, CA
slyon at pacificnet.net

----- Original Message -----
From: "Fred Wittman" <wittfa19 at EARTHLINK.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Thursday, October 17, 2002 2:03 PM
Subject: HR-1680


I've tinkered with a 1680 that I picked up from eBay, it was beset with
intermittent problems, almost all of which were solved by removing the
boards and cleaning the fingers.  I did this trial and error, using no-ox,
alcohol, sand paper (fine grit) and even a pink pearl eraser.  First
question:  Anyone have a method they've tried and perfected for such a
problem?  Second question:  With this 1680, there is a noticable
degeneration in audio quality (the base disappears) when the function switch
moves from LSB to USB, and no change at all from USB to CW.  My hunch is
that it's miswired.  Any ideas?  Thanks in advance.  Also, many thanks for
the schematics, to all who answered my request.

Fred Wittman

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