Repairing vintage computers is bread-and-butter for many of us around here. The machines themselves tend to be fairly fixable, assuming spare parts are available and there hasn’t been too much physical damage. Peripherals can be another matter, though. Since they interface with the real world they can have more esoteric problems that aren’t always solvable. [joekutz] was handed just such a device in the form of a CE-150 docking station for a Sharp PC1500 Pocket Computer, which has a plotter built in. Here’s his “tip” for getting plotters like these working again.
The first step here is to disassemble the original, dried out pens to scavenge a few of the parts. The outer case needs to be kept so that it can be put back into the plotter, and a small O-ring is saved as well. To replace the dried-out tips [joekutz] discards the original tips and replaces them with tips from a common ink pen, using shrink wrap tubing to help fit the pen’s tip into the original plotter cylinder. He also takes the ink from the pen to fill the plotter’s cartridge, completing the surgery on the multi-colored plotter and bringing it back to life.
Of course this build goes well beyond the plotter, including bringing the PC1500 back to life as well. There are a few other videos about this project covering that original restoration as well as demonstrating some of the quirks of how this computer is meant to be programmed. But we mostly focused on the plotter here since that is a little bit out of the ordinary, and we’re also sure that refilling ink cartridges of any sort gets under the skin of everyone at HP.
To be honest, I’m not impressed by the plotting quality of fineliners at all. The tips are basically fibers and dragging them across the paper deforms them, which translates to imprecise plots. And you can clearly see it in the video.
I think the only kind of pen that gives a good quality output will be a rollerball pen.
Note that rollerball and ballpoint pens are different, ballpoint pens have a thick oil-based ink, rollerballs a thin water-based ink that flows much easier. Easier flow means less drag when dragging the pen over the paper, and so means greater accuracy.
@RetepV I think gel ink would work too, viscosity is comparable to rollerball ink, nowhere near the goo used in cheapo BIC pens
Rapidograph is even better.
In a technical drawing it makes no sense, but in writing these distortions have their charm/style.
OTOH ballpoint ink won’t run if the paper accidentally gets wet. I got into endless trouble in a medical environment for signing forms with a non-ballpoint pen for this reason!
True. But I do think the ink of the original pens of the CGP-115 was water-based.
And I hope then that nobody uses inkjet printers in a medical environment… ;)
I have a few radiograph pens for my HP-7475a. However, you can’t use those in those little plotters. The pens are horizontal in the holder, and the ink would leak out. On an HP-7475a, the pens are held horizontally, and the ink will stay in, while gravity and probably capillary action pulls the ink down onto the paper.
Meh. A plotter like that has never been built for precision. There is probably some slop in a lot of different parts in the mechanism. But the big dots where lines start are not looking good.
Or you just view it from another perspective. It’s got it’s own style.
I can tell you that it actually is quite good. And the paper feed roll has small needles that actually prick through the paper and pin it in place so that it doesn’t slip.
I agree that the quality could be better :) . You pointed out one reason already, the other reason is that the original pens have cone-shaped tips that sit in holes in the end-plate of the cage which centers them whenever they are pushed onto the paper. My solution here does not have a good cone shape. But for text and my graphical examples here it did not matter that much and I was happy to see the old thing working again.
I have that! I had to replace the rechargeable batteries for my dad about 20 years ago. He used it with a program to size air conditioners for houses. I’ll have to pull it out of the display case and see if it’s still viable.
Curious whether it still works then! Hope the batteries did not leak out in the 20 years, I got very lucky with mine.
I wanted one of those plotters so badly when I was a kid, we had one at school, interfaced to the BBC micros and I remember seeing them in, I think, Radioshack.
Could watch them working all day, which was handy because they were so slow.
CGP-115 was my first ‘printer’ largely because it was all I could afford. I submitted one of my term paper assignments printed with it; lol. I did at least cut the long scroll and pasted into two-column format on conventional A sized paper.
Me too. The Tandy CGP-115 had a centronics interface, so could connect to any centronics parallel port.
But basically I hardly used it. ;) Ok, I used it at some time to plot PCB layouts. It’s so long ago that I don’t remember anymore, but I think I wrote a piece of software that would convert from some plotter format (I guess HP-GL?) to CGP-115.
But well, if you plot a PCB layout for making a PCB, you have to magnify it by 4x to make the contact films for exposing the PCB. So for a 10×15 cm PCB (Eurocard), your print would be 20×30 cm, and you needed two pieces of paper (which were 11.4 cm wide).
At school we had a proper HP-7475a, and basically I just gave up on the effort and plotted my PCBs in school, for a small sum. ;)
Now I have my own proper HP-7475a. But never use it. ;) My screen is much larger than A4, and zooms in and out easily, and I just make gerbers and let JLCPCB figure out how to make a PCB from it. :D
But to be honest: I am still charmed by this small plotter.
Had one of those back in the day, in fact there is still a tube of the pens rolling around in my top desk drawer. The plotter itself died when one of the plastic drive gears off of the motor split and I could never repair it or find a replacement.
Do you still have it? Jeff Birt commissioned brass replacement gears for the ALPS DPG1302 plotter mechanism (the one in the CGP-115.) The pens are still available too (I just bought some last year) although they’re sold by one website based in Germany and are pretty pricey.
Forgot to add, see this sites: http://tandy.wiki/CGP-115, and https://www.soigeneris.com/alps-printer-plotter-mechanism-pinion-gears
I recognized the plotter from the thumbnail. Alps were common plotter of the mid 80s, being made available for a number of computers including Commodore 64 and Tandy. Even a Sega game system from Japan has the same mechanism.
One of the common problem with the Alps plotter is a small gear, they tended to crack. 3D printed replacement saved my Commodore 1520 and it works to date.
Before taking my unit apart I read that the gears are prone to failing. I got lucky, but I was worried that my gears die throughout making the three videos. I love the idea that someone makes new brass gears for these old units.
If anyone wants a real challenge, I have a Calcomp 960 Vertical Plotter just rotting in a barn. It looks complete aside from any terminal to control it. Just do a Google image search for “Calcomp 960 Vertical Plotter” and a picture I posted years ago on Reddit should be one of the first results.
Where is the barn?
https://www.heise.de/ratgeber/Make-Projekt-Computer-als-Datasette-betreiben-5045127.html
Wow I missed that one ! :) also: Thank you, paywall -.-