Classic HP forums?? - plotter questions
ard at p850ug1.demon.co.uk
Thu Jun 28 17:33:34 CDT 2007
> I got no bites the first time, so I'm trying again.
> Does anyone know of any good classic HP forums,
> sites, or parts sources?
I've already mentioned my favourite site for old HP manuals in a
> I need to construct an interface cable for my
> recently acquired HP7202A flatbed pen plotter.
> This plotter was manufactured around 1971 and
> could be interfaced using one of three styles of
> interface cables (it appears that they all plugged
> into the same male adapter port on the back of
It's not unheard-of for HP to use external interface circuitry. The
serial port on many of their older termianls, and one some HP9000/200
stuff, was a 5 0pin microribbon connector. It carries the normal RS232
signals at RS232 levels, so a simple cable will link it to a nromal DB25
RS232 device, But there are also power lines on that 50 pin connector,
and from waht I've read, HP sold (at least) an RS422 interface, a current
loop interfave and a 300 baud modem that plugged into said connector and
drew power form it.
I asusem that;'s not hte case with your plotter though.
> the unit, but must have used different pins). I
> plan to use the 20mA style of hookup, which I
> assume will use four of the pins. I just need
> to determine which of the pins are used for the
> 20mA send and receive. Other options were for
Does the service manual contain schematics? If so, it should be easy to
find out which pins are used.
If you have the problem of having to trace the signal through various
cables and adapter PCBs to get it from the logic to the exernal
connector, then I recoemnet tracing it on the actual hardware (if only to
be sure). Use an ohmeter to check continuity from, say, the optoisolator
for current loop receice to the read panel connector
More information about the cctech