HP Draftmaster RX pen plotter needs love

[Michael Newton]

That's right, there is a -5v test point that reads zero.

Any guidance? Like if I need to pull parts off and test them, which ones
might I go for? I'm a caveman with electronics.

M.


On Fri, Nov 11, 2016 at 9:17 PM, Pete Lancashire <pete at petelancashire.com>
wrote:

> Are you saying there is a -12V test point and there is nothing there ?
>
> If +5 is 400mV high, that's not dangerous but it is something I'd take care
> of first.
>
> -pete
>
> On Fri, Nov 11, 2016 at 8:35 PM, Michael Newton <michael.newton at gmail.com>
> wrote:
>
> > 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.
> > > >
> > >
> >
> >
>