HP Draftmaster RX pen plotter needs love

Michael Newton michael.newton at gmail.com
Fri Nov 11 17:36:53 CST 2016

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

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?


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