In article <3A29724F.2FEA@ames.net>, Dr. Gerald N. Johnson, electrical
engineer <geraldj@ames.net> writes
>Sounds to me as if the socket pin or a trace is going open between the
>chip and the key connector.
Thanks for the thoughts Jerry - much appreciated. There is good
continuity between paddle contacts and chip pin - pin 19 is pulled to
ground by the paddle, even when the keyer doesn't respond with any
dashes.
Granted there could be a problem with the external pull-up resistor,
although it wouldn't explain why it sometimes doesn't respond to pin 19
(the dash pin) being grounded by the paddle.
When the keyer is sending uncontrollable dashes, pin 19 sets itself to
just above ground - which suggests to me an internal chip problem. Maybe
something along the lines of a thermal crack, as you suggest, but it
would be worth holding another pull-up resistor in place whilst the
fault condition exists.
Anyway, I know how hard it is to comment on somebody else's rig
problems, without having the rig in front of you, but thank you again
for spending the time to float your ideas, which are very valid.
--
72, peter g3xjs
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