Sunday, 15 October 2017

RetroChallenge 2017/10: Part 5

NEC PC-8401s' Capacitors & NiCd Sorted

Since discovering the leaky capacitors in the PC-8401s LCD module (last post, Part 4), I've replaced the problem components and the screen is now working without further issues. So, while had the main case opened I also decided to replace all the other potentially problem components and give the unit a good service.

I replaced all the capacitors with like for like values. The one exception being a 1200uf 25v, which is now a 1200uf 35v variety. The extra voltage level is not an issue, though the replacement capacitor is twice the length of the one it replaced, luckily there was space to lay it on it side.

The other remaining problem component was the 30 year old NiCd battery, which amazingly hadn't vomited it's guts all over the motherboard. The NiCd battery inside the PC-8401s is there to keep the DRAM and system clock ticking over should there be no main battery or indeed mains power. (No compact flash for 1985 user convenience).

1 Frand Super-Capacitor Battery Replacement

I decided to replace the battery with a 1 frand 5.5v super capacitor. I've previously made similar modifications to my Tandy M100 and M102 machines to good results, with RAM storage remaining intact for over a month before (until I got board waiting) I reapplied mains power. Similarly to the previous m100 modification, I bent the pins of the capacitor over horizontally before attaching wires which are the soldered on to the PCB. The capacitor itself is attached to the circuit board with double sided tape, keeping very firmly in place.

So next time it's back to doing something else arguably useful with a 30 year old computer.

See RetroChallenge IntroPart 1Part_2,  Part 3Part 4, Part 5

Wednesday, 11 October 2017

RetroChallenge 2017/10: Part 4

My NEC PC-8401s' LCD Module Faces Capacitor Issues

I'd noticed, well couldn't help noticing really that the PC-8401s' LCD screen would flicker, and every now again turn off unexpectedly after extended use. Over the last week the occurrences became more frequent. Interestingly or comfortingly the screen flickering has no effect on the Main Computer, everything stays resident, you can even continue typing while the screen is off. So what ever the problem? It is appeared localised to the LCD screen. Time to pry open the computer and see what's happening.

A quick look over the main board revealed nothing of immediate concern, though at some point I'll want to replace the NICAD backup battery and the 30 year old capacitors, thankfully though none of these components have been leaking. Semi confident the main board is okay it was time to crack open the LCD bezel, not the most convenient thing to do.

NEC PC-8401 Main Board

Unlike the main case the bezel is mostly held together with molded plastic clips, taking it apart took some considerable carefully spent time. Once off however it was immediately clear where the problem (hopefully the only problem) lay.

NEC PC-8401s' LCD Panel

We've got 2 exploded leaky electrolytic capacitors that need to be replacing, and while we're at it the other 10 should be swapped out for good measure. I guess considering the age of the computer this is not unexpected, all this is really part of the excitement of playing around with old hardware.

Some Picturesque Leaky Electrolytic Capacitors

Well then, before continuing any further it's of the the electronics supplier to procure some of these tiny caps, of which I have exactly none of in my parts draw.

As a quick aside the panel was manufactured by Epson.

Back view of the NEC PC-8401s' LCD Panel

See RetroChallenge IntroPart 1Part_2,  Part 3, Part 4, Part 5

Sunday, 8 October 2017

RetroChallenge 2017/10: Part 3

NEC PC-8401's Software-To-Go on the Go

It's time try out some of the PC- 8401's inbuilt software. Ideally I'll be wanting to create files that are usable outside the NEC PC-8401 1980's bubble. The software included in ROM was all quite cabable for the time our NEC was realeased into the wild, we should be able to make use of it to some extent today.

There are four software packages provided in ROM:
  • Wordstar-To-Go: Micro Pro's word processing package, a portable version of the Wordstar. 
  • Calc-To-Go: Portable version of Calc Star, also by Micro Pro. 
  • Personal Filer: A flat file database program.
  • Telecom: Modem and Serial communication tools.

Of those, the two packages likely to be of most use in the modern context are Wordstar-To-Go and Telecom and I'll quickly look at those now. Telecom is arguably of most importance as it will be required to move files and additional software on and off the computer. The limited 64k of available RAM (32 for storage and 32 as active memory) makes Telecom a necessity if we plan on doing anything useful in the longer term.

Getting the files on and off with Telecom

The Telecom application is quite effective, and thankfully includes the XModem transfer protocol, making file transfers reliable. Connecting to a regular PC requires a USB to serial cable and a NULL modem cable. Nothing odd here, I used standard off the shelf parts.

PC-8401 and LINUX CuteCom Talking
For software on the modern LINUX computer I'm using CuteCom as it's a windowed terminal communication program, the command line based Minicom works just as well for this though.

I found the default Telecom configurations need some tweaking. The baud rate was best set to 1200 for plain ASCII file transfers and terminal emulation, else the buffer got full and text was lost. For XModem the baud rate value can be up to 19200 (with some issues), 9600 provides issue free transfers. Other than that I set Stop bits to 1, as is the default value for just about everything else out there. The configurations can be saved to memory, so once setup it's all good to go next time.

XModem transfers in both directions work perfectly, making the task of installing software and transferring other files a simple.

With a basic configuration setup all the networking capacity of 1985 is at our fingertips. If I want to take the PC-8401BM out on a field trip, or write up blog pages on the go, then we can rest easy knowing all that hard work is easily transfered back to a regular PC.

With basic communications configures it's time to look at using some of the built in productivity software.

NEC PC-8401BM Telecom Default Configuration
CONNECTIONRS-232CInternal Modem or RS-232C
PROTOCOLOFFON for modem7 / xmodem, OFF for ASCII transfers
SPEED9600150 - 19200 baud
WORD LENGTH87 or 8 bits per character
SI/SOONShift In/Shift Out sequence
STOP BITS21, 1.5 or 2/td>
PARITYNONO,EVEN,ODD,IGNORE. Ignore only effective when STOP BITS set to 8
PPS1010 or 20. Pulse Per Second, Used for modem dialing
LABELOFFON or OFF. Displays the Function key values
LF SUP.ONON or OFF. ON Suppresses LF codes ignored during uploads
LINE DELAY01 - 7. Delay ACK response.
PRINTOFFON or OFF. Echo session on a printer
SAVEOFFSave Telecom configuration on exit

Can we Wordstar-To-Go?

Wordstar may still be a perfectly usable as word processor, with one proviso, that we have some sort of document conversion utility. This is where we start running into problems on the modern PC side. It seems that we're now so far removed from Wordstars historical dominance in the marketplace that pre-existing conversion tools, even thoughs designed for 'newer' platforms are themselves so out of date emulation is required to run them. (I find this news a touch disturbing).

Over at the Way Back Machine (love that machine), the remains of the WordStar Resource Site provides downloads to various converters, Sadly, I've tried a number of the conversion utilities without any luck this far. They all specify conversion capabilities extending to DOS and Windows Wordstar files exclusively, so the PC-8401s Wordstar-To-Go files will need to undergo a CPM to DOS conversion first.

Failing conversion utilities, there are two other options available, both built into our trusty PC-8401. Firstly, Wordstar-To-Go can produce simple text files that need no conversion. This is the easiest option to use.

The second options is available during file transfers. When sending files with the Telecom package there is an option to convert Wordstar files to plain text. This produces a similar result to using plain text to start with, but not quite. Conversion ignores continuous paragraphs, so what appears to be the end of a line in a Wordstar file (lines are by default 65 character long) is the end of a line, meaning all paragraphs would have to reformatted to be contiguous. Note that Wordstar itself treats paragraphs the same way. The text will appear  exactly as formatted on screen in Wordstar, minus control characters and .dot commands.

The best explanation is a simple example, below are three version of the same file. The text was justified in the Wordstar formatted files.

RAW Wordstar File: 
Thå  quicë  browî dingï jumpeä oveò thå lazù  fox®  Thå  kangaroï 
jumped over the dingo.

No animals were harmed in the above test sentence.

Wordstar File with Special Characters Removed During File Transfer
The  quick  brown dingo jumped over the lazy  fox.  The  kangaroo 
jumped over the dingo.

No animals were harmed in the above test sentence.

 Plain Text File
The quick brown dingo jumped over the lazy fox. The kangaroo jumped over the dingo.

No animals were harmed in the above test sentence.

So is Wordstar on the PC-8401 still usable in the modern context? Yes, but with some serious limitations for the time being. There would be an interesting RetroChallenge project in writing a decent conversion utility.

See RetroChallenge IntroPart 1Part_2,  Part 3Part 4, Part 5

Monday, 2 October 2017

RetroChallenge 2017/10: Part 2

An NEC PC-8401 Quick Guide Book for the Internet Archive

As we know from the previous blog entry, there was absolutely no documentation on the NEC PC-8401BM contained within the Internet Archive. Today I thought it might be a good idea to start addressing this situation.

PC-8401BM Manuals
I have in my possession the 4 Australian Manuals and the Quick Start Guide originally packaged with the PC-8401BM. The easiest of these to scan and make available to the Archive is the Quick Start Guide, this being the only book conveniently with a ring style binding. So naturally I've started here.

Being in a spiral binder the pages were easy to remove, this has allowed for quite a nice scan overall. The other manuals however are going to be slightly more of a challenge to pull clean copies from. So after an hour or so plus some cleaning up time, I'm happy to report the Quick Start Guide is now available to all those who seek it's wisdom.

I should say the Guide is mostly available, there are unfortunately 2 pages missing, pages 34 and 35. These pages should form the first part of the Calc-To-Go section in the book. Not the best of situations, still the rest of the book is complete and pretty much gives all the information the casual PC-8401BM user is likely to require.

I'm not quite sure on the best way to proceed in scanning the remaining books. All the manuals are in exceptional condition, as such I don't wish to ruin them by either pressing the books to firmly against the scanner and cracking the spines, or indeed by removing the spines. It certainly would be handy to have access to a book scanner. (If anybody out there is feeling generous, please send your best book scanner free of charge ASAP).

As a bonus, I thought I'd clean up one of the pull out / fold down sections of the Guide illustrating the many extended devices NEC produced to dock and otherwise attach to the PC-8401BM. These include Data Recorders, Disk Drives, RAM Cartridges and CRT / Monitor adapters. The product codes of all these items is conveniently listed. For those interested in acquiring computer extensions today, the NEC product codes it could well make Ebay and Craigslist searches a little easier (you could try NEC directly in some sort of vain last hope of course).

The PC-8401BM Connection of Peripherals fold out, because everybody loves a good diagram.

The Guide Book is now avaliable and indexed at the Internet Archive:

See RetroChallenge IntroPart 1Part_2,  Part 3Part 4, Part 5

Sunday, 1 October 2017

RetroChallenge 2017/10: Part 1

The NEC PC-8401 a Starlet in the Press?

NEC PC-8401A Review in Creative Computing Magazine
The NEC PC-8401, AKA the Starlet premiered at the November 1984 Comdex show, a year after the Tandy Model 100 made its splash. (As an aside, glimpse the Model 100 at the 1983 show in this remarkable footage). The rise of the portable computing has begun, and a new world order soon to be dominated by IBM compatibility is starting to play out. Where does our little NEC offering fit in?

Unfortunately for us, there are scant references to the PC-8401BM in its contemporary computer press, or so it would appear by the lack of articles available on the internet archive. This is a trend that continues, even against the current rise of 'retro' computing within the global consciousness. The 1984 Comex appearance of the PC-8401 is however noted in Infoworld 1984-12-17 magazine.

That the PC-8401 lacks a perceptible public success may not accurately indicate it market penetration, particularly considering its main reason for being was to serve a business oriented market. It is therefore not so unsurprising that hobbyists of the period may have ignored the PC-8401 as expensive business machine, with that the business positioning still limiting any appeal for today's retro collectors or enthusiast.

The only extensive review of the PC-8401 from the time period available over at the Internet Archive is a write up in the March 1985 issue of Creative Computing Magazine by David H Ahl's. The review is based around the model PC-8401A not the PC-8401BM which I'll be using over the course of the RetroChallenge.

Overall the Creative Computing review is a positive one, with the only major criticism levelled at the small display area on the Model 8401A, an issue addressed on the 8401BM. The included software, built into the machines ROMS is noted favourably, Wordstar-To-Go which is found to lacking in some of features available in the desktop version, a minor let down and scores only reluctant approval.

Interestingly what we could surmise as the reasons behind the failure of the 8401 to enter the popular consciousness are highlighted at the end of the Creative Computing article. Firstly NECs failure to include BASIC in ROM at once precludes the machine from hobbyist usage. While the lack of programming languages provided by default on computers today is a non-issue, in 1984 this was often the pathway for home hackers to explore a computers capacities. Secondly, and more interestingly it seems NEC had a less than stellar marketing division (at least outside of Japan).

In retrospect, NEC should possibly have paid close attention to Creative Computing closing summary, as now the trail and magazine reviews go cold. There are of course many gaps in the Internet Archives collection of 80s computer magazines, even so the range of coverage still available and the lack of NEC PC8401 mentions in them would seem to confirm David H Ahl's concerns.

Luckily the target business market did procure and use enough PC-8401s that they haven't all gone to landfill, and somehow a PC-8401BM even managed to keep it's manuals intact, make its way to me and so we'll have something more to examine for the month long RetroChallenge.

The rather colourful NEC PC-8401BM User Guides.

See RetroChallenge IntroPart 1Part_2,  Part 3Part 4, Part 5

Friday, 29 September 2017

RetroChallenge 2017/10: Getting to know the NEC PC-8401BM

It's almost time for RetroChallenge 2017/10, a month long opportunity to focus in on a single project, share and document your activities and finally share the results with the wider retro community. This sounded like a good excuse for some retro adventure, so I've thrown my hat into the ring and decided to spend the time focusing in on the portable 'powerhouse' that is the NEC PC-8401BM.

Portable computer out in the wild
My NEC PC-8401BM in the wilderness, Compute anywhere with 1985 style.

Strangely there is very little information on the inter-tubes about the NEC PC-8401BM, AKA the NEC PC-8401A and AKA NEC Starlet. As luck would have it one has fallen into my lap very recently, and just in time for the Retrochallenge.

During October I'll explore this tidy 'little' laptop styled machine, examin the available online articles, work through the machines manuals and generally explore how this computer can be used today, practically or otherwise.

Exact outcome unknown, we'll end up where curiosity takes us.

See RetroChallenge IntroPart 1Part_2,  Part 3Part 4, Part 5

Sunday, 24 September 2017

The TRS-80 Model 100 MyTeSed is Alive

After a bit of a wait the MyTeSed for the TSR-80 Model 100 enters the construction stage. A simple SD card reader is in sight, though not until a few challenges are met. Mostly the build went smoothly, mostly being down to one misguided assumption in turn inducing lot of time spent waiting.

TRS-80 Model 100 and a Model 102 with SD Card Reader Interfaces
Two MyTeSeds, one attached to a Model 102 and the other connected a Model 100

This is the first time I've had PCBs produced by a fabrication house, for every other project I've made them myself. The end result is a really impressed impressive sight, and the quality is quite amazing. The quality of the PCB lends a certain confidence to the endeavour of populating it.

Construction started out quite simply, first mounting all the loose components onto the PCB. A snag to the master plan appeared when it came time to mount the SD card module. I'd soldered some header pins to the PCB and added a couple of layered of doubled sided tape to hold the module firmly. The header pins I would very soon have to remove again.

I had assumed I'd be able to de-solder the right angled header pins from the micro SD module and then attach the module to the pins I'd soldered onto the main PCB. This of course turned out to be a very bad idea, leading ultimately to the complete destruction of a module. It seems the modules PCBs just aren't up to that kind of meddling. The lesson here I suppose is to never assume anything will work quite as planned.

My misguided assumption cost me a couple of weeks, I only had the one SD module to break, I found myself needing toprocure some more modules from China, leaving me floundering before proceeding any further. Oh well, live and learn.

A little wiser and with some new modules in hand, the easiest solution to my problem was to attach some cutoffs to the bottom of of an SD card module and then solder those into the PCB mounting holes as originally intended. I'd probably choose to mount the modules in the same way next time around as it worked near enough to originally planned.

I'd sensibly procured a number of spare SD modules, so decided to build up a second MyTeSed, allowing me to make one very minor change. The first build used a full length 26 pin IDC socket, this really isn't needed as there are only 3 pins in use, from pin 1 to 3 (GND,TX and RX). I switched to a 10 pin IDC socket, this makes the IDC cable a lot easier to construct, a lot easier to connect, easier to move around and ever so slightly cheaper to build (if a few cents are of concern).

Lastly I mounted the Arduino Nanos, I chose to solder the first Nano directly to the initial PCB build, on the second board I mounted on a couple of pin sockets first. This second option is the recommended choice if planning to re-use the Nanos' in other projects, though I figured I'll have at least one of these SD readers around for some time to come.

 The good news is that after all the waiting for parts the end result worked as expected. The only really major component of the initial project left to sort out is software, again as I'd managed to kill the original SD module I had nothing to test with until I got to this point. I've subsequently had some time move forwardon that, which will form the basis of the next post.

2 Versions of the TRS-80 Model 100 SD Card Reader Interface the MyTeSed.
The two versions of the MyTeSed, the first build with full 26 pin IDC cable (9v and battery attached)

Thursday, 17 August 2017

Model 100 micro SD Card reader, the MyTeSed

After the initial testing with a full sized SD card reader shield and Ardunio Uno, I wanted to know how easy it would be to shrink the TRS-80 Model 100 SD card interfaces size down to something a little more acceptable. I thought about building the whole design from the ground up, in the end the abundance of cheap modules from China can't be beaten on price (or convenience).

Before getting into the excitement of the details, the other major half of the fun of building these projects is naming them, so I'm calling this interface the 'MyTeSed', standing for My Model 'T' Serial Drive. Now that out of the way, on with where I'm up to with the project to date.

Testing the functionality of the MyTeSed on a Breadboard 

The Hardware

I've gone with a Arduino Nano for the heart of the project, the footprint of the Nano is barely larger than a atmega328p chip and far smaller if including the ancillary components. The Nano also nicely takes care of power regulation, has a USB port for easy re-programming, and behaves identically to a Uno. Thus making the Nano one of the most inclusive of the reduced sized Arduinos' to use.

Micro SD Card Reader Module
The revised hardware also substitutes the full sized SD card shield with an all in one micro USB card module. The SD module accommodates either 5v or 3.3v signals, making it an ideal choice for use with the Nano. It's a standard module avaliable from just about anywhere, including Ebay and various online Chinese merchants of all things electronica.

After a little experimentation I've also decided to set up software serial on pins D8 and D9 of the Nano. Using software serial as the conduit to the T100 / T102 / T200 leaves the Nanos' standard serial pins D1 and D2 free to use as a pass-through (actually via the Nanos' USB) which will be used as direct connections to a PC. As in the previous version (blog entry Using SD Cards with the TRS-80 Model 100) a MAX323 IC handles the RS232 to TTL serial conversion.

The when complete the MyTeSeD can be powered from a 6v to 9v battery supply (like most Arduino projects), in addition usage of the Nano conveniently provides a means to power the interface via the mini USB port, allowing battery packs or a USB power source etc.

MyTeSed Circuit Diagram

Arduino Code

This is not by any measure the final code to be using with the interface, for the moment it serves as proof of concept. I'm still yet to go back a write up a more permanent solution, it does however work for now, just expect some drastic changes for the foreseeable future.

In essence the current idea is for MyTeSed to listen for instructions in plain text over the serial line, 'LOAD' and 'SAVE' for example, then either send data back or shift files around on the SD card. Regardless there is a lot left to implement, such as file deletion, access to directories and error checking.
// **************************************************************************
// **** MyTeSed: T100 SD Card Reader for Arduino Nano and SD Card Reader ****
// **************************************************************************
// ** David Stephenson 2017-08-23  **
// ** Version 0.01                 **
// **********************************
#include <SPI.h>
#include <SD.h>
#include <SoftwareSerial.h>


const byte LF=10;
const byte CR=13;
const byte EF=26;

SoftwareSerial mySerial(12, 13); // RX, TX

class CardReader {
  SERIAL_MODE eSerialMode = FREE;
  //DRIVE_COMMAND eDriveMode = NONE;

  File MyFile;
  String sFileName;
  String sInString;
  unsigned long TimeLastUpdate = 0;
  // Class Private Functions
  void LoadBas() {
   char cRead, cLast;

   if(eSerialMode == DATA_OUT){
    MyFile =;

      if (cRead== LF){
       if (cLast != CR){
      } else {
       cLast = cRead;
    eSerialMode = FREE;

  void SaveBas(char cInChar) {
   if(eSerialMode == DATA_IN){
    if(cInChar != EF){
    } else { 
     eSerialMode = FREE;
  void FilesOut() {
  void commandIn(){
   String KEYWORDS[7] = {"LOAD","SAVE","KILL","FILES","MOVE","CP2SD","CP2R"};
   String sInSubString;



   if (sInString.length() >= 3){
    for (byte bKeyword = 0 ; bKeyword < 8 ; bKeyword++){
     sInSubString = sInString.substring(0,KEYWORDS[bKeyword].length() );
     if (sInSubString.indexOf(KEYWORDS[bKeyword])!=-1){
      if (KEYWORDS[bKeyword] == "LOAD") {
       sFileName = sInString.substring(4);
       eSerialMode = DATA_OUT;

      else if (KEYWORDS[bKeyword] == "SAVE" || KEYWORDS[bKeyword] == "CP2D") {
       sFileName = sInString.substring(4);
       if (SD.exists(sFileName)) {
       MyFile =, FILE_WRITE);
       eSerialMode = DATA_IN;
      else if (KEYWORDS[bKeyword] == "FILES") {
       eSerialMode = FILES_OUT;

   //sInCommand = false;
   sInString = "";
 void SerialIn(char cInChar){
  switch(eSerialMode) {
   case FREE:
    if(cInChar == CR){
     eSerialMode = COMMAND;
    } else {
     sInString += cInChar;
   case DATA_IN:


CardReader MyCard;

void setup()

  // Open serial communications and wait for port to open:
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only

  // set the data rate for the SoftwareSerial port

  } else {

void loop()
 char cInChar;
 if (mySerial.available()) {
  cInChar = (char);
  //sInString += cInChar;

Talking With a Model 100

Saving, loading and copying files from the micro SD card requires first sending a command and a filename to the serial port, then engaging the normal BASIC save / load to serial command. The COM port should be set to 1200 Baud, 7 Bit Word length, Ignore parity.

For example, saving the active BASIC file:

Or loading a BASIC file from the Interface:

Possibly the easiest method to save or load  BASIC program is to add some of the below lines to a program listings. Alternatively an option once the code base is a little more on the stable side would be the development of a menu-ing  system, but that's for latter.

Save a BASIC file to SD Card

910 PRINT #1,"save"
920 CLOSE 1
930 SAVE "COM:57I1D"

Load BASIC file to SD Card

20 PRINT #1,"load"
30 CLOSE 1
40 LOAD "COM:57I1D"

Copy a RAM Text File to the SD Card

50 LINE INPUT #1, Z$
60 PRINT #2,Z$
80 GOTO 50
90 PRINT #2, CHR$(26)
100 CLOSE 1: CLOSE 2

Copy a File from the SD Card to a RAM Text File

50 LINE INPUT #2, Z$
60 PRINT #1,Z$
80 GOTO 50
90 PRINT #1, CHR$(26)
100 CLOSE 1: CLOSE 2

Next Time

The next stage of proceedings is to design a circuit board, should be a simple enough task. Unlike all the other projects in this blog I'm planning on getting the PCB produced by a fabrication house, and hopefully all that will go well.