"N_Cook" wrote in
:

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

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?

I think that the computer senses when a voltage is present on the
power jack. I think it then asks the supply 'who are you'. If the
supply says 'I am an 85 (or whatever) supply', the computer is happy.
If it doesn't reply or says 'I am a low wattage supply', the computer
gives an error message.

I base this on the fact that the error message appears when I plug in
my 'broken' power supply to the computer OR when I plug the supply
into the AC, but not when I plug in a 'good supply' although the
'AC/battery indicator' changes when either supply is connected.












--
bz 73 de N5BZ k

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

Could not that be done totally within the pc
Within a few seconds of connecting and normal loading is ok try
maximum load for a fraction of a second and if
undercurrent/undervoltage then display error message




it's probably just a resistor value that gets read,forms a voltage divider
and the developed V gets read. Simple,cheap to implement.
No resistor,you get the "insufficient supply" message.

--
Jim Yanik
jyanik
at
localnet
dot com