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.