Technology and retro computer blog

Epson HX-20 Revival

I recently saw an Epson HX-20 for sale on a local trading site, what initially caught my attention was that it had an integrated printer and micro tape drive.  Very cool!  Not knowing much about these machines I did a bit of research on it and was impressed to hear it's considered the first laptop.  I generally like to collect machines that have some historical significance, and limit my main collection to stuff from the late 70's and early 80's.  It fit the bill nicely, so I snapped it up.

Epson HX-20
Epson HX-20 with case
Epson HX-20 lcdscreen


  Epson HX20 specifications
  Manufacturer      Epson
  Release date   November 1981
  CPU   Two Hitachi 6301
  Speed   614 kHz
  Ram   16k to 32k
  Rom   24k (3 x 2764, 8k eproms)
  Storage   Cassette internal 
  Expansion   1 optional 8k 2764 eprom slot 



  Rom basic


 120x32 pixel LCD display



SkiWriter rom   SkiWriter rom


As is quite common with these old machines it was untested and had no adapter, but it's condition was great and it came with the hard case and an extra eprom.  I was hoping that getting it running would be as simple as finding a suitable adapter, I have an adjustable multi-fit adapter which did fit but on initial tests it wouldn't power on.

From reading posts on various sites, I found that these machines require a functional internal battery to operate even with the adapter plugged in.  So I proceeded to take it apart and found not surprisingly that the internal NiCd battery had perished (see pic above).  Luckily the leakage of the batteries was contained within the plastic wrapping of the battery pack.  The corrosion had also made it's way up the battery leads and started to lightly corrode the connector on the motherboard, but the board connector was easily cleaned. 

I removed the battery and cut off the battery leads, they were totally corroded and could not be saved.  I tried removing the battery leads from the connector on the lead side, but they were stuck with corrosion.  So I soaked the connector in white vinegar for a couple of hours and was able to remove the corroded leads.  I made up new leads using the wires from a pc 3.5" floppy connector.  The floppy connector pins fit perfectly into the HX-20's battery lead connector. 

Prior to making up new batteries, I was eager to test whether the machine worked, so I connected my adapter directly to the battery leads and plugged it into the mother board. I set the adapter to 4.5v and the machine came to life!  The adapter I have is voltage switchable but is only 300ma.  There wasn't enough power to run the tape drive or the printer but I could run Basic and enter in a simple Basic program.  Three items were displayed on the lcd: 1 Monitor; 2 Basic and 3, there was an optional rom installed called Entecard.

I found the posts below which discuss making a new battery pack for the HX-20:

I managed to find the exact same batteries at my local parts store, so I made up a new battery pack and attached the new leads.  I partly re-assembled the machine with the new battery and plugged in the  adapter and was able to monitor the battery voltage.  I saw the voltage on the battery going up as the adapter was powered, so this was a good sign that the batteries were charging. 

I fully re-assembled everything and after a few hours of charging I was able to get both the printer and the micro-tape drive working!  The printer ribbons that came with the machine were long dead but replacements are still widely available.  The printer paper is also readily available as it just uses 2.25" cash register paper.  There was also an original Epson micro-cassette that came with the machine which still reads and writes ok.

Now that I had a fully functional machine I started looking for software that would run on it.  There's plenty of Basic programs available on various sites, but the main one I wanted was Skiwriter.  It then occurred to me to check the extra rom that was supplied with the machine, and it was an original Epson Skiwriter rom.  It was in a sealed plastic bag so it may have never been used.  I removed the rear plastic cover replacing the installed Entecard rom with the Skywriter rom. On power-up I was greeted with the Skiwriter option on the menu.

Skiwriter ROM

Skiwriter is a word processor application for the HX20.  The zip file below contains an image of the Skiwriter eprom in both .bin and .hex versions.  To use Skiwriter on your own HX20, create a 2764 8k eprom using either the .bin or .hex image file. (14.06 kb)

Skiwriter Manual

This is the only electronic copy of the Skiwriter manual known to exist.

Comments (2) -

  • Geoff Barnard

    2/06/2016 2:38:57 AM |

    Done anything with your HX?
    Mine, which I bought new early 80s as my first computer, is still working, just about.   I also have the TF-20 disk drive, although the two units now don't communicate, and I've not sorted that out - yet!
    I have the HCCS Forth ROM installed, the Forth works quite neatly.   I have the code for the ROM extracted, which I assume could be transferred to another EPROM?
    Best wishes,
    Geoff, Guisborough, England

  • Theo

    2/06/2016 3:45:11 PM |

    Hi Geoff,

    I've written some basic programs on the HX-20 and I also tinkered with creating a serial cable for it to connect to my pc.  That didn't work so well, something to do with the wiring of the cable.  I'll revisit that at some stage.

    Forth sounds interesting, email it to me if you can.  Yes, you can create EPROMS for use in the HX-20, you need to use 2764 8k eproms.


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