TI Travelmate

J.C. Wren jcwren at jcwren.com
Wed Mar 1 20:37:01 CST 2006

    According to this page, <URL: 
 >, it is indeed center positive.   "ZVC36-18-D4" appears to be the 
model number for the brick.


John C. Ellingboe wrote:
> "John C. Ellingboe" wrote: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'?
>> -tony
> 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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