John C. Ellingboe
john at guntersville.net
Wed Mar 1 20:07:31 CST 2006
Tony Duell wrote:
> > On 3/1/2006 at 3:07 PM John C. Ellingboe wrote:
> > >Does anyone have information on the TI Travelmate LT220/V. A
> > >quick Google didn't turn up anything of value.
> > >
> > >I have acquired one with a pile of other items and have no idea
> > >how useful it might be. The power source, 18V DC did not come
> > >with it and there is no indication as to whether the center pin
> > >of the power connector is the positive connection or not.
> > Any external I/O connectors on it? Things like parallel port connections
> > will usually have their ground/return pins conected to the - side of the
> > power supply.
> While this is normally reliable, be warned it doesn't _always_ work. The
> HP48 calculator has the signal ground pin of the (minimal) serial port
> connected to the +ve supply line. There's an internal voltage converter
> which doubles the logic supply, the transmit data pin swings between
> this doubled supply voltage an logic ground, so about -5V to +5V wrt the
> logic +ve line which is the RS232 signal ground.
> > Last resort is popping the box open and checking the ground plane on the
> > PCB or any of the ICs (if the ground plane is buried) against the
> > connector.
> That's the one I do first. Why 'as a last resort'?
I have raised the cover to look at the LCD and keyboard, checked
that the battery compartment doesn't have any battery contacts
in it and that it has three diffrent connectors for io and maybe
a buss extension. I haven't had time to open the case or
otherwise check anything out. As I said, a quick Google didn't
turn up anything as a starting point.
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