I finally solved a problem with my Omni C digital
display.
The display would track frequency but the "f" segment
of each LED digit would stay on or other segments
would light on an erratic basis.
After trying quite a few things including resoldering
all the connections on the bottom of the display logic
PCB, I finally noted that the display would abruptly
turn normal if I freeze sprayed one of the CMOS to LED
driver chips (75491). When replacing the chip and
checking the surrounding components didn't help I
noted several thru hole studs mounted in the PCB.
Apparently Ten-Tec didn't use thru hole plating but
inserted miniature studs to do the job. There were
several of these studs near the suspect chip. After
resoldering the TOP surface of the PCB around these
studs, lo and behold, the problem was solved.
I resoldered every remaining thru hole stud on the
logic board.
Thus if any other folks have similar problems, check
those stud solder joints. It's not very obvious during
an initial inspection. The studs look just like
component leads protruding thru the PCB. Also, at
least two of the studs are UNDER nearby resistors. I
had to pull the resistors to gain access to those
studs.
73,
Doug/WA1TUT
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