TI Travelmate

Tony Duell ard at p850ug1.demon.co.uk
Thu Mar 2 12:28:11 CST 2006

> If this were a desktop system, I'd go for the screwdriver first.  However,
> on portable systems, reassembly can sometimes get a little involved--at
> least for my "all thumbs" hands! 

SOmetime I forget that not everyone had a mis-spent childhood 
re-assuembly clocks and ASR33s :-)
> Let's not forget that the original poster knows that the PSU puts out
> +18vdc.  It's EXTREMELY unlikely that the positive side of the PSU has a
> direct connection with any signal pin!

I'ev got at least one cheap serial printer where the +ve side of the PSU 
(about 10V regulated) is connected to the +5V line. There's a 7905 
regulator, the output of which is the logic ground line. Then the 
unregulated input formes a -5V-ish line for the (discrete transistor) 
RS232 driver.

It's unlikely a computer would do the same thing, and it's unlikely that 
you'd find the +5V line on a normal serial or parallel connector. 

I would bet a sizeable amount that if yo u can find one side of the power 
connector connected to a pin you know to be ground (e.g. pin 7 on a DB25 
RS232 port) then that is the -ve side of the power connector.


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