bz wrote in message
98.139...
"N_Cook" wrote in
:

....

not found a www ref specifically to that Compaq DC polarity.
Did just DVM the blue lead back to the mains connector and 1.3M regular
resistance back to mains ground pin, nothing showing on any other
routes.


Some of these supplies use I2C communications to 'tell the computer about
the power supply capabilities'. Without the I2C communications, the
computer may complain that the supply doesn't have sufficient capacity to
charge the computer's batteries.

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

Would a data stream be observable on the third wire from the ps at switch on
and disconnected from the pc or only after a RTS chirp or something from the
pc when connected?