Today I present to you the Silver Reed EB-50. Made in 1985, this thing has a bit of an identity crisis. It’s a printer, a plotter and a typewriter all in one. The reason I got it was because it uses the same tiny ball-point pens that the Commodore 1520 printer/plotter uses. However, this prints on normal 8.5″ wide paper. It’s also very portable, has a lid that covers the keyboard and a flip out handle. It can run on batteries (5 x D cells OMG heavy) or on DC 7.5V power (center negative in case you want to know). For $9.99 it was a bargain curiosity that I couldn’t pass up.


In normal typewriter mode, you press a key and it will “draw” that character in one of 3 sizes, styles or directions in one of 4 colors. You can position the print head anywhere you’d like to print text. In addition, there are function keys to create graphs, right on the typewriter. Pie charts, bar graphs and line graphs are simple– select the type, enter the data points and it prints a graph at the print head position. Pretty clever for something that works sans computer.

Switch it to printer mode and now a computer takes over via the parallel port. This is where things got weird. I found reference to someone that wrote a program to convert HPGL plotter files to ones that printed on this one. This was key since there was no manual and I ran out of internets. But the file was locked up in a “drivers” ad supported nightmare of a website that had me install some bullshit driver manager on Windows to “install” a C code source file. What-fucking-ever. It’s included below in you want it.


A quick Processing sketch later and I’ve produced some output on it from my Mac using an old PowerPrint serial to parallel adapter via a KeySpan USB to serial adapter. Lots of adaptation, but what do you expect from a nearly 26 year old printer.

# hp2eb50.c
#include <stdio.h>

#define SCAL(x) (((x)+halfscale)/scale)
#define NUMV(x) ((x)=='-' || ((x) <= '9' && (x) >= '0'))
#define SP ('S'<<8)+'P'
#define PU ('P'<<8)+'U'
#define PD ('P'<<8)+'D'
#define PA ('P'<<8)+'A'
#define IW ('I'<<8)+'W'
#define SC ('S'<<8)+'C'
#define LB ('L'<<8)+'B'

FILE *source, *plotter;
short c,i,j,pen,scale,x1,x2,y1,y2,hx,hy,halfscale;
short befehl,ende,rot, colour[] = {0,1,2,3,0,1,2,3};
char param[100], *output;

void upcase(s)
   char *s;
  {
   register char c;
   register int  i=0;

   while ((c = *(s++)) && i<99)
     {
      param[i++] = (c>='a' && c<='z')? c-'a'+'A' : c;
     }
   param[i] = 0;
  }

short get_num()
  {
   register short c,x=0;
   short s;

   if (ende) return(0);
   else
     {
      while(((c = getc(source)) & 0x1ff) <= ' ');
      if (c == '-')  
        {
         s=-1;
         c = getc(source);
        }
      else s=1;
      while (c >= '0' && c <= '9')
	{
	 x = x*10+c-'0';
         while(((c = getc(source)) & 0x1ff) <= ' ');
	}
      if (c == ';') ende = -1;
      return(x*s);
     }
  }

void rotate()
  {
   register short h;

   if (rot)
     {
      y2 = y1;
      h = x1; x1 = y1; y1 = -h;
     }
  }

main(argc,argv)
   int argc;
   char *argv[];
  {
   if (argc<2)
     {
      printf("Usage: %s <hpgl-file> [SCALE <scale>] [ROT] [COLOUR <n1..n8>] [TO <output filename>]n",argv[0]);
      exit(0);
     }

   rot = 0;
   output = "par:";
   for (i=2;i<argc;i++)
     {
      upcase(argv[i]);
      if (!strcmp(param,"ROT")) rot=1;
      if (!strcmp(param,"SCALE") && i<argc-1)
	{
	 scale = atol(argv[++i]);
	 if (scale == 0) scale = 1;
	}
      if (!strcmp(param,"TO") && i<argc-1) output = argv[++i];
      if (!strcmp(param,"COLOUR") && i<argc-1)
	{
	 for (i++,j=0;j<8;j++) colour[j]=(argv[i][j]-'0') & 0x03;
	}
     }
   halfscale = scale/2;

   if (!(source = fopen(argv[1],"r")))
     {
      puts("Sorry - Can't open file!");
      exit(0);
     }
   if (!(plotter = fopen(output,"w")))
     {
      puts("Sorry - Can't open output file");
      fclose(source);
      exit(0);
     }

   pen = 0;
   fputc(18,plotter);  
   puts(" Command no.:");
   j = 1;
   do
     {
      i = ende = 0;

      do
	{
	 c = getc(source);
	} while (((c < 'A') || (c > 'Z')) && (c != -1));
      befehl = (c==-1)? 0 : (c & 0xff)<<8 | (getc(source) & 0xff);

      printf("2331A23313C %5dn",j++);   

      switch(befehl)
        {
         case SP : {
		    x1 = get_num();
		    if (x1)
                      fprintf(plotter,"C%d;n",colour[(x1-1)&7]);
                    break;
		   }
         case PU : {
         	    pen = 0;
		    break;
		   }
         case PD : {
		    pen = 1;
		    break;
		   }
         case PA : {
		    while (!ende)
		      {
		       x1 = SCAL(get_num());
		       if (!ende)
			{
		  	 y1 = SCAL(get_num());
			 rotate();
		         if (pen==1) 
                             fprintf(plotter,"D%d,%d;n",x1,y1);
		           else 
                             fprintf(plotter,"M%d,%d;n",x1,y1);
			}
		      }
		    break;
		   }
	 case LB : {
		    fputc('P',plotter);
	            while((c = getc(source)) >= 32) 
		      putc(c,plotter);
		    putc(13,plotter);
		    putc(10,plotter);
		    break;
		   }
         case SC : {
		    x1 = get_num();
		    if (ende) break; 
		    x2 = get_num();
		    y1 = get_num(); y2 = get_num();		    
		   }
         case IW : {
		    if (befehl==IW)
		      {
		       x1 = get_num(); y1 = get_num();
		       y2 = get_num(); y2 = get_num();
		      }
		    hx = (x2-x1+999)/1000;
		    hy = (y2-y1+999)/1000;
		    hx = (hx>hy)? hx : hy;
		    if (scale<hx)
		      {
		       scale = hx;
		       halfscale = scale/2;
		       printf("New scale: %dn2331A",scale);
		      }
		    rotate();
		    fprintf(plotter,"M%d,%d;nI;n",SCAL(-x1),SCAL(-y2));
		   }
        }
     } while (c!=-1);
   fputc(17,plotter);
   fclose(source);
   fclose(plotter);
   puts("nReady.n");
  }

NOTE! Split gears causing causing or plot errors? New replacement Alps gears for the Commodore 1520, Atari 1020, etc are now available! Click here to order your set.

My first computer was a Commodore VIC-20. I got it as a Christmas present from my parents in 1982. I’m pretty sure they picked it up at Montgomery Ward, which was still around at the time. Shortly there after, I got my first printer to go with it. A Commodore 1520 Printer Plotter.

This printer was great. Firstly, it was tiny for a printer. It was smaller than the computer! Everything about it was tiny. It used tiny 4.5″ wide paper that was on a roll. It used tiny ball-point pens (yes, pens!) of four colors that it could selectively choose. I used it well, mostly printing nonsense I’m sure. Time passes and the printer disappears. I think I may have “taken it apart” which for me at that time usually meant destroying it. In any case, the original never followed me.

Fast forward to 2001 when I bought two from eBay. One came with the box and some extra pens (which proved to be the most elusive consumable). But irritatingly, the printer seemed to have fits when it was asked to print something. The motors would make an unpleasant noise and the print head would vibrate in place. The paper advance was also acting up.

Upon further inspection and some help from the interwebs, I found the culprit. A very tiny gear connects the stepper motor to the rest of the gearing to move both in the X (print head left and right) and Y (paper up and down). These two gears, made of nylon or plastic, have shrunk over time and split, causing the teeth of the gear to get jammed. Commodore sourced the plotter mechanism from ALPS (as did Tandy, Atari and Mattel for their plotters). Likely all plotters using this mechanism are suffering the same fate. Frustrated, I shelved it.

Fast forward to 2009 when I take a course in historical computers, I decided to revisit the printer to see if I can repair it. I found a terrific resource on a Commodore 128 forum from user “airship” he calls The 1520 Plotter Survival Guide written in 2007. It lists sources for the paper, the pens and possible help in fixing the gears.

To fix the gear issue, I decide to take the repair route. A company called Electronic Goldmine has the ALPS plotter mechanism (surplus) that Commodore used (at $1.49 ea!). I buy 10, hoping that at least a couple of the gears will be good. All of the gears are split– time has not been good to them. But the good news is the mechanisms make great replacements if the original motors are bad. Plus it gives me 20 gears to try and fix various ways.

To repair the gears, I first remove them from the stepper motor. They’re just pressure fitted so they slide off. I used some super glue to fix the split back together and clamp it together overnight. I then use a 1/16″ drill bit to drill out a tiny amount of the center of the gear. This will relieve the strain and prevent further splitting when the gear is back on the motor shaft. Next, I dry test the gear on the motor and see if it works. If it does, I use super glue to attach the gear to the shaft.

The result:

It works! I keyed in a demo program from the manual and produced this:

Coming up in another post I’ll show you what it looks like when it plots text (with slow motion video).

NOTE! Split gears causing causing or plot errors? New replacement Alps gears for the Commodore 1520, Atari 1020, etc are now available! Click here to order your set.