HP 7475A PLOTTER

HP 7475A Plotter

The HP 7475A plotter, introduced in 1983, is a 6 pen plotter. It is capable of wide format, is relatively fast, and strikes the right middle between the smaller HP 7470 or 7440, and the very fast but positively huge HP 7550. It speaks HP-GL, which is easy to generate.

A few programs still support HPGL output, most notably Inkspace, KiCAD and DWGTrueView 2013. Several vintage HP test instruments also can plot a hard copy of their display graphics directly to it. WINLine still makes a plotter driver that works on Windows 7 and 10, and in principle should allow you to plot directly from your application: https://www.winline.com/. However I do not recommend it. Aside from being very expensive, I got poor results on everything I tried, with very slow and un-optimized plotting, but the killer were the very many plotting errors and artifacts. In fact nothing I tried did plot correctly. I got far better results by importing vector drawings into Inkscape, exporting it to an HPGL file from there, and sending the file to the printer via a terminal emulator.

The resolution is amazingly good, provided you have good pens *and* good paper with low bleed. It is not good at all with standard inkjet paper which is made to absorb ink and makes big blots. Original HP plotter paper works best, the matte back of modern photo paper is a good alternative. Even though the HP 7475 is quite a fast plotter, it still takes forever to print something that has a lot of filled areas and curves in it. It is very fast for just straight geometric lines.

Videos

In this video I demonstrate the HP 7475A by plotting the internal demo and also a drawing of the space shuttle Columbia. Furthermore, I demonstrate how to send HP-GL commands directly from the terminal interface. The HP 7475A is actually quite smart and can draw a lot with just a few commands.

Dried out pens are always an issue when dealing with the HP plotters. In this video, I show how to revive old pens.

Dried out pens are always an issue when dealing with the HP plotters. In this video, I show how to revive old pens.

In this episode, I repair the Geneva wheel that failed and prevented the pen carousel from spinning. I also demonstrate schematics and PCB plotting using KiCAD and Inkscape.

Documentation

The Interfacing and Programming manual is of particular interest, as it contains the description of the HP-GL commands that the plotter supports.

Plot Files

Geneva Wheel

Here is a dimensioned drawing (not from me, just retrieved from the web), and the STL file that Mike Stewart made for 3D printing the part.