Thanks to all who offered help.
I have found the problem. It was a loose mounting post; the "odd" one which
did not make an appropriate ground on an isolted section of the board. When
I tested the voltage on the chip, I discovered that the board was loose. I
am the one who mounted the board - "self taping" screws not tightened enough
to bring the board flush to the third standoff. When the first two mounts
on the other side of the board are tightened, the board is rigid but rises
slightly above level; the third mount requires enough pressure to bring the
board back to level. Not knowing how much pressure to put on the screw and
not paying close enough attention resulted in a faulty ground: "human error".
Not a big deal - but the age old lesson - check your work.
Without instructions, the replies to my post were very helpful in knowing
that no adjustment was required. That forced me back to my work to take a
second look: before I made further error in unnecessary adjustments.
Thanks again for the help. Much appreciated.
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