HP Draftmaster RX pen plotter needs love

[Michael Newton]

Thanks for the encouragement. I'm going in.

I found test points on the power supply/motor driver board as detailed in
Chapter 12 of that manual.

+5v, +12v, +15v, +42v and +85v are all there (and all .4v high or so)

But there is no -12v. That seems relevant.

The capacitors all look OK to the naked eye.

Actually diagnosing and repairing electronics is new territory for me, but
I suppose this is where I read up, maybe pull that board out, and start
testing diodes and caps.

Thanks again Alexandre - and if you or anyone else has any clues to narrow
it down, please share.

M.




On Fri, Nov 11, 2016 at 3:38 PM, Alexandre Souza <
alexandre.tabajara at gmail.com> wrote:

> How is the power supply? All rails ok? Input/output capacitors not bulged
> nor leaked?
>
> 2016-11-11 21:36 GMT-02:00 Michael Newton <michael.newton at gmail.com>:
>
> > I acquired a working HP Draftmaster RX (HP part # 7596B).
> >
> > An awesome machine, 36" roll feed and 8 pens, complete with several pen
> > carousels, user manual, and hundreds of working pens.
> >
> > I was very excited to make a splash in the art world with this thing. I
> did
> > get it to perfectly draw a 3 color demo page from the front panel.
> >
> > Thereafter it started displaying errors on the display such as "200"
> which
> > means it needs "mechanical calibration".
> >
> > Thanks to hpmuseum.net I acquired the service manual
> > <http://www.hpmuseum.net/document.php?hwfile=1292>, which catalogs many
> > calibrations and self-tests to run from the front panel, including the
> > aforementioned "mechanical calibration".
> >
> > So I power up with the appropriate front panel keys depressed to run this
> > calibration. The paper drive motor starts making noise, but the paper
> > rollers aren't turning, and the LCD display is blank.
> >
> > Since that moment, the LCD display is always blank so it is currently a
> > boat anchor.
> >
> > It's a terribly sad state of affairs. I have basic electronics and
> > mechanical skills and an oscilloscope so following the troubleshooting
> > procedures in the manual I might be able to identify a part to replace.
> But
> > of course, parts for sale online are are rare, expensive, used and
> probably
> > untested.
> >
> > Probably better would be lower-level repair of whatever parts are faulty
> > but that's probably more than I can manage at my skill level.
> >
> > I'm in Seattle, WA. Is there anyone alive in the pacific NW who will pay
> a
> > visit and help me fix this thing? (The only company I found that admits
> to
> > working on pen plotters is 360tech in Austin, TX.)
> >
> > Or someone elsewhere I could ship electronics parts to for test and
> repair?
> > Or provide guidance, or help in any form at all?
> >
> > thanks
> > M.
> >
>