Build a Junior

Thw design of the Elektor Junior is well documented in the Elektor articles, books and other articles like the KIM Kenner. In many languages, the archive here is as complete as possible, but you could see some pieces of information in only one language section. The hardware components for the most part are not exotic, especially for the time of publication.
The software in the form of (sources of) the ROMs and applications such as Microsoft Basic and even Operating systems like OS65DV3 is also easy to find.

So with all this information available it is no surprise to see modern versions of the Junior. Some try to stay as close to the original design, others just take the ideas and implement it in a more modern an d convenient way.

Some obstacles in building a Junior are:

  • the original PCB’s are only available as low quality magazine articles quality. And even then be careful, the original article mixed up front an back!
  • the EPROM for the Junior monitor is a 2708 UV EPROM. A very old hard to get part, hard to program and requiring power supplies like -5V and +12V besides to usual +5V.
  • the expansion card used a 82S33 PROM for the address decoding. Also an obsolete part and hard to program.

So what designers can do:

  • design the PCB’s again. Kicad e.g.
  • replace the 2708 with an EPROM like the 2716 or bigger or an EEPROM like the 28C16 or bigger
  • use a GAL or discrete logic for the 82S33
  • use a modern SRAM IC and increase RAM memory a lot
  • modify the address decoding to fit the modern ROM and RAM
  • obtain parts like the 6502, 6532 and 6522
  • replace the hard to get 1 MHz crystal with a can oscillator
  • simplify the power to +5V

Here are some examples of builds:

Junior with KB9 and OS65DV3.3

With thanks to Philippe Roehr from France I present on this page how he got KIM Basic 9 and Ohio Scientific OS65D to work on the Junior

Junior build

Philippe has build a Junior system with at least a main board, an expansion board, 16K Dynamic RAM board expanded to 64K and a floppy controller.

It started with the Junior itself, followed by the expansion card, The monitor software PM and TM were tested.

Floppy controller, RAM card behind.

Junior KB9 Basic

Philippe started with the KB9 binary from the KIM-1 pages.
Philippe then applied the process outlined in the Elektor articles to adjust Basic to the Junior character I/O routines and also improved the speed by adjusting the now unnecessary code that took care of the ROR bug in early 6502’s.

Philippe transferred the binary to the Junior with Ed’s utility KIMTape, producing a KIM-1 audio wave file. The Junior accepts this format, a bit slow but only needed once. After seeing all was well, Philippe wrote the now optimized Junior KB9 Basic to audio wave file, and made a hex dump on the terminal. I picked up the dump, a captured text file form a a terminal emulator, and wrote a conversion program to produce a binary.

All the files here: archive with audio wave file, dump on terminal, binary and conversion software.


After building the Junior, having PM and TM monitor working well, KB9 Basic operational, the next step Philippe took was getting the operating OS65Dv3.3 operational.
He took the steps described by Elektor in the articles with some modern additions.

A Junior able to run OS65DV3.3 needs an expansion card,  a RAM card (his is 64K) and the Elektor floppy controller, which is identical to the OSI one (6850 + 6820 ICs)

Instead of a real floppy drive Philip used the hardware Gotek floppy emulator with the Flashfloppy firmware. And used the manuals images of, and the OSIHFE utility described in the OSI Web forum posts.

Elektor made a bootstrap eprom (ESS515 download here, source in Paperware 2) able to
* load OS65D (V3.1 or 3.3 as far as I know) from floppy
* give basic I/O capability (RS232 and floppy)
* manage hex display and keyboard
* modify OS65 for the hex display after the very first load to fully adapt them to the system ( about 10 bytes to modify)

Here the OS65DV3.3 disk image in native and Flashfloppy format ready to use.

During the second part of december 2020 Philippe added a real floppy controller and added the Ascii Video Terminal (new version of hackaday). With improved moter control of the floppy drive!

VDU board with OS65D

PMV for OS65D source checked by Philippe Roehr



A program, SerialTester,  a guide and test results.

Also updated Prolific PL2303HXA driver misery solution.

Serial USB adapters testing

So I have a collection of those USB to serial adapters, some with cables and DB-9 connectors, some with cable and Dupont connectors, and some USB TTL type connectors on a PCB with male or female Dupont pin connectors for USB-A, mini or micro USB. Most not documented or unsure if the voltage levels are 3.3V or 5V ..

First some background. These are all descendants of the EIA RS232 standard in some way. Terminology, asynchronous serial format, voltage levels, start bits, stop bits, 7 or 8 data bits, hardware and software handshake, and the way it is abused in many of these devices. And so common nowadays in Arduino and ESP8268, ESP32 and even Raspberry Pi world.

If you are new to the serial world and want to use these devices and understand how, study the next chapter. You will learn and know what I am talking about: DCE, DTE, DSR, DTR, TxD, RxD, CTS, RTS, DTR, RI, CarrierDetect, UAR/T’s, TTL voltage levels being reverse to RS232 voltage levels, a ‘0’ being negative RS232 voltage up to 15V, a ‘1’ being as low as -15V.


RS232 asynchronous information

This picture shows where RS232 came into being about 50 years ago,

Read these PDF’s:
RS232 Protocol – Basics
EIA RS232-C Standard Protocol
EIA RS232-E Standard Protocol
Fundamentals of RS–232 Serial Communications
RS232 Physical Layer Interface Standards
RS232 (TIA/EIA-232-F)
RS-232: Serial Ports

USB Serial TTL devices

These little devices came into use to communicate with small computers like SBC’s, Arduino and ESP’s and PC’s. Throw out the overhead of the + and -15v, limit or leave out the handshake signals, (mis)use the DTR signal to reset the Arduino, use it to download firmware or collect data from sensors on the small computers and process it on bigger machines. And act as the power supply the little computer.
Based on special UAR/T IC’s, very small footprint, and dirt cheap.

Testing USB Serial TTL adapters

What you need:
– A PC, Raspberry Pi or another Linux or Windows PC. Any PC platform supporting USB ports will do.
– The program SerialTester, see below
– A small breadboard
– A collection of Dupont cables with male and female connectors
– A multimeter, a most simple one will do


Testing USB serial adapters is not that difficult, you need a terminal emulator, which are available in lots of formats and capabilities. Putty, Minicom etc all allow to choose a serial port, set baudrate and other parameters like hardware handshake, software handshake, number of data and stop bits. With a loopback test (which means connecting serial out TxD to serial in (RxD) you can test the serial connection by typing characters and seeing the characters appear on screen.

What I miss in these programs is a way to inspect the modem control lines. So I wrote a little program for that.
SerialTester allows to do the loopback test and shows the state of the modem control lines.
You can change the DTR and RTS lines since these are set of cleared by the USB serial port. The other lines are read from the USB serial adapter.

Get the program here:
Windows 10 installable executable
source (Lazarus + Freepascal) and executable for Windows, Linux and executable for Raspberry Pi

Use the program as follows to completely test and document (write down test results on the next steps!) the adapter.

1. It is a GUI/Windows program, so start as usual on your operating system. Raspberry runs this program fine, but Linux is not so forgiving in plug and play of USB devices, so expect some hangs and reboots. CH340 chipsets can have a temper, and SerialTester sometimes fails, where Minicom succeeds.

2. Insert the USB adapter, do not connect anything yet to the adapter
For the USB-A types it is handy to have an USB-A male -female cable to bring the adapter to the table

– Check if the USB adapter is recognized by the operating system
For Windows start Device Manager and look for COM Ports, like COM8 in the example below
On Linux start a terminal and type “lsusb”, insert the USB serial adapter and look for added USB device serial adapter, in the screenshot an FTDI adapter.
The command “ls -l /dev/ttyUSB*” will show devices like “ttyUSB0”.

3. Click Port settings and click in the field Port drop down button. A list of serial adapters will be shown, pick one. Note that on a Raspberry the serial port ttyAMA0 on the GPIO connector will be shown also. Here we want the ttyUSBxx device.

Select 300 baud as baud rate, this will help seeing the transmit with the multimeter., leave the rest default.

Press OK

4. Open the Port by clicking the button Open Port. Look at the status displayed, it should tell the port is opened. If not opened, you might have a driver problem, see the sections below on CH34x, FTDI and Prolific 2303HX devices.
You will also see the DTR and RTS fields light up red, as opening also sets the DTR and RTS pin high.

5. Switch on the multimeter and read the prints on the USB or the color of the wires.
– First find Gnd. Indicated with the label GND or a black wire.
– Now find Vcc, indicated with VCC or the red wire. Measure the voltage, should be 5V, 3.3V. Some adapters have a jumper to select the voltage. Some adapters also change the voltage on the other lines, some do not. Measure!

6. Find the TxD pin. Connect the multimeter to the TxD pin. It should be +3.3V or 5V. Also check if changing VCC to +3.3V or 5V makes any difference, some adapters do, some do not change the voltages on the pins.

7. Enter a long string in the Send field, and press Send (or Send CR for a line ending). Observe the readout on the multimeter, it should be lower than the value in rest. Nothing will be shown in the received fields.

If not, then this is not the transmitting pin. Check RxD if that is the transmitting pin, for all my adapters it was TxD, but who knows what manufacturers do ..

8. Inspect the adapter for a DTR line if any. Connect the multimeter to the corresponding pin and measure the voltage. Press the DTR button in SerialTester and check if the voltage changes on the pin.

9. Repeat for the RTS line.

10. Locate the RxD line. Connect this line to the TxD pin and send a string again. Now you should see the Receive and Receive hex fields filled with the send string.

11. Now if any pins are not tested yet, they have to be the other modem control lines. The labels on the adapter will tell or experiment and measure. Connecting to ground or VCC with a 2k2 resistor (to be safe) will show on the display of the SerialTester program the corresponding level.

Chipsets: FTDI, Prolific, Silicon Labs, CH340

The USB Serial adapters contain a UAR/T IC, made by a small group of manufacturers.

1. FTDI. Comes with the highest recommendations. Many types. Well supported in Linux and Windows.
Due to fake IC’s made in China the current drivers check and try to make a fake inoperable.
If you encounter in Windows a non-working FTDI adapter, you cna only use it in Linux, after ‘repairing it. See here how to do that

2. Prolific. Supported in Linux and Windows.
Also due to fakes, older (not fake!) IC’s made by Prolific are not supported by the current Prolific driver in Windows. Device manager shows PL2303HXA PHASED OUT SINCE 2012. PLEASE CONTACT YOUR SUPPLIER.

Easy to solve with an older version of the drive, like in this archive. Unpack in a folder, Update driver, Look on this PC, Have disk, Browse to the folder.
Windows may ‘update’ the driver again, just rollback the update in Device Manager. For permanent fix, see also this page how to enable group Policies on Windows 10 Home and prevent any updates.

3. CH34x. I sometimes encounter problems under Linux with this chipset. Windows runs fine.


‘Blue’ closed connector with cable
Prolific PL2303
Male Dupont connectors
Black Gnd
Red +5V
Green Tx (sending data) 3.3V
Yellow Rx (receiving data)
Betemcu CH340
Status LED red, send LED blue
Edge pin connector maleGND Gnd
VC +3.V or 5 V slide switch
TX 5V Sending
Rx 5V receiving
CTS connect ground for ‘on’
Button switch of Vcc
D-Sun-V3.0 CH340
Status LED red Send blue led Received blue led
Edge pin connector male
RxD receiving
TxD sending at 3.3V or 5V
3V3 3.3V
Vcc jumper to +3.3V or 5V (no jumper 3.3 V)
5V 5V
Tienu ZX2H1911A1 PL2303HXA
Status LED red Sending green LED Receiving Yellow LED
Edge pin male
5V 5V
3.3V 3.3V
TxD sending 3.5V
RxD receiving 3.5V
Gnd Gnd
Red status LED send receive green LEDs
Edge pin male
Jumper +5V Vcc +3.V
Jumper 5V – Vcc – 3.3V
All modem signals to edges RI CTS RTS
110 baud not supported
DTR 5V or 3.3V following jumper
TX sending 5V or 3.3V following jumper
RX receiving 5V or 3.3V following jumper
VCC 5V or 3.3V following jumper
CTS 5V or 3.3V following jumper
Gnd Gnd
4D Programming Cable CP2102
Dupont female
Gnd Gnd
Tx Sending 3.4V
Rx Receiving 3.4V
+5V 5V
FTDI cable no ident,
lights in cable red (receive) green (send)
Dupont female
Black Gnd
Blue CTS 3.4V
Red +5V
Green Sending 3.4V
White Receive 3.4V
Yellow RTS 3.4V
Tienu FTDI232H
USB-A FTDI edge pin red status LED green send, yellow receive
RXD Receive at 3.5V
TXD Sending at 3.5V
3.3V 3.4V
5V 5V
FDTI basic Sparkfun female dupont bottom
Mini USB
5V 5V
TxD sending 5V
RXI receive 5V
Square CP210X Red status
LED Red LED send Red LED receive
Micro USB Male Dupont Edge
3V3 3.3V
DTR 3.4V
RXD sending 3.4 V
TXD receive 3.4V
+5V 5V
FTDI232 Mini USB
Jumper 5V – Vcc – 3.3V
All modem signals to edges. Voltages follow Jumper setting.
MBC2 cable Prolific 2303
black GND
red 5V Vcc
Green TX sending at 3.4V
White Rx
UC-2102 Cable CP210X
Male edge pin connector
DTR 3.4V
TxD sending 3.4 V
+5V +5V



Elektor Junior Book 3 added

Thanks to Joan from Barcelona I have added book 3 of the Elektor Junior range.


Elektor Junior computer large update

After finishing the large update a month ago of KIM-1/SYM-1/AIM 65 I turned my attention to the Elektuur/Elektor archive, mainly the 6502 period of 1978 to 1985 where the SBC Junior Computer and EC65/Octopus systems were introduced.

New and enhanced in higher quality information about these systems:
– published in multiple languages and more content of articles and books scanned, not only dutch bnut also English, German, French, some Spanish and Italian.
– better hardware descriptions and photos of PCBs etc
– more complete software library, sources of systems ROMS etc.
– gallery of Juniors, EC65 and other cards and cases

Start here for the Elektor/Elektuur/Junior/EC65/Octopus pages.

Junior retronics articles

Elektor did write about the Junior and related designs in recent years, retro electronics! This site (at the present and previous wwww locations) was mentioned also.

Oh, and this is retro but not a Junior computer!

Elektor gallery

Elektor Literature

6502, Junior and EC65(K)/Octopus publications by Elektuur and Elektor 1978 -1985 and the magaizines KIM KENNER and COMPUSER

Books and Paperware Junior Computer, Dutch, English, German, French, Italian
Articles from the magazine Elektuur and Elektor 1978 -1985
– Nederlands
– Engels
– Deutsch
– Francais
The dutch KIM/6502 Club published many articles on the 6502 and the Junior: KIM 6502 Kenner archief


4 “De Junior” door Anton Muller

KIM KENNER 13 – 18 oktober 1980

4 Hex teller en flip flop voor de Junior, J. Hummeling
6 Ervaringen met de Junior computer, W.L. van Pelt

KIM KENNER 14 – 20 december 1980

4 JUNIOR, H.J.C. Otten
8 One armed Bandit voor de Junior, F.J. Butterfield
12 Ervaringen met de Junior, J. van Sprang en W.L. van Pelt
14 Junior leesroutine voor Kansas City cassette interface, Sebo Woldringh
16 Junior schrijfroutine voor Kansas City cassette interface, Sebo

De 6502 KENNER nr 15 maart 1980

13 Ervaringen met de JUNIOR J. van Sprang en W.L. van Pelt
15 Letters en cijfers op JUNIOR display J. Hummeling

De 6502 KENNER nr 16 mei 1981

24 Ervaringen met de Junior, W. Van Pelt en J. van Sprang
26 Automatische register uitlezing voor de Junior
39 Browse voor de Junior

De 6502 KENNER 17 – augustus 1981

12 Ervaringen met de Junior, Willem van Pelt en John van Sprang

De 6502 KENNER 19 – december 1981

Schrijf- en lees routine voor de Junior, Dick Blok
15 Rapportcijfer, Rein Duyts
22 Display op oscilloscope, C. Totte
28 Aanpassingen aan de Macro Assembler van C.W. Moser, van Nieuwenhove Koen
34 Patches op Basic, Hans Otten
35 Lichtshow voor de Junior en de KIM, K. Kikke
38 4 kolom printer, A.S. Hankel
40 Printer routine voor H14, Paul de Beer en Hans Otten
43 Break voor Junior en KIM, Frans Mepschen

De 6502 KENNER 20 – februari 1982 LUSTRUM nummer

79 SYM Microsoft Basic aangepast voor de Junior, door Jaron Orenztajn
81 Aanvullingen voor de Elektuur EPROM programmer, door John van Sprang
85 Aanpassingen Junior print voor 2716, door J. Vollering
86 Bugs
87 Patches Micro Ade deel 11 voor de Junior, door A. Hankel
91 Voedingsschema voor +5V, +12V en -12V. door Frans Smeehuizen
92 Memory test aangepast voor de Junior, door Bert van Tiel

De 6502 KENNER 21- Mei 1982

36 Junior’s aan de PET, door Ruud Uphoff

De 6502 KENNER 22 – Augustus 1982

12 Patches op KIM-1 Basic t.b.v. de Junior, door Van Nieuwenhove Koen

De 6502 KENNER 23 – Oktober 1982

11 Patches op KIM-1 Basic t.b.v Junior (deel 2), door Van Nieuwenhove Koen
25 R.T.T.Y. met Junior, Telexberichten via korte golf op uw scherm, door A.S. Hankel
32 Easy Editing Supporter v. Junior, door R.C. Vissers
40 Simpele geheugenuitbreiding, door H. Burgers
43 Single Step Debug Programma, door M. A. v.d. Laan
46 Tiny Basic voor Junior + cassette routine, door Filip van Kenhove

De 6502 KENNER 24 – December 1982

14 Patches op KIM-1 Basic t.b.v Junior (deel 3), door Van Nieuwenhove Koen
4 Cassette bibliotheek, Junior cassette 2

De 6502 KENNER 25 – Februari 1983

6 Patches op KIM-1 Basic t.b.v Junior (deel 4, slot), en bugs in deel 1,2 en 3, door Van Nieuwenhove Koen
24 Junior en dubbel adressering VIA 6522, door Koen van Nieuwenhove
35 AIM-65 Basic voor de Junior, door E.J.M. Visschedijk

De 6502 KENNER 26 – mei 1983

4 ReNr en Append voor de SYM-Basic voor Junior
6 Maak van Junior een Senior: Disk drive Systeem van Proton op Junior, door P. Franssen
16 Printen op OKI Microline 80 Printer, een nieuwe printer routine voor Junior

De 6502 KENNER 27 – Augustus 1983

3 Proton’s JUNIOR DOS
3 Spiraal (KIM) nu voor Junior
19 Koppeling van Junior aan 8″ Floppy, met FD1771 controler 8″ single en 5″ double density, door Koen van Nieuwenhove
41 UART schakeling voor Junior, door A.A. Zwart


KIM KENNER 28 – Oktober 1983

6 Grafisch display voor Junior, door H. Christen

De 6502 KENNER 29 – December 1983

21 Read Junior’s SYM-Basic cassettes with Microsoft KB9 Basic
22 Toevoegen niruwe commando’s aan de SYM-1 Basic voor KIM-1 en Junior, Frans Smeehuyzen
25 Vraag en aanbod
26 Automatisch regels verwijderen, Frans Smeehuyzen
28 Boekennieuws
28 Clear screen voor JUNIOR’s SYM-1 Basic, Will Cuypers
29 Tekstverwerker, naar een idee van M.A. van der Laan
31 Hexadecimaal omzetter, Dick Blok
33 Universele geheugenkaart voor Junior
33 KB9-Basic op Acorn SYSTEM-1
39 Junior’s Hex monitor on Acorn-System, Alfons van de Meutter

De 6502 KENNER 30 – Februari 1984

8 Usurpator, schaakprogramma voor Junior, Fridus Jonkman
9 PACHA, patch on PM monitor, Fernando Lopez
11 Bouw eens een Miljonair: 2 miljoen bytes voor uw Junior, Jam H. Vernimmen
17 Program cassette 1: Junior/Apple formaat cassette routines deel 1, A Brouwer
34 LED’s op Junior, Hans Buurman
37 Uitbreidingen op SYM-1 Basic voor KIM en Junior: automatische regelnummering, Frans Smeehuyzen
39 Missing data in Junior Book 4
47 Load your Junior Sym-Basic Tapes into KB-9

De 6502 KENNER 32 – Juni 1984

21 KIM-1 en Junior KB-9 Basic Tokenized Microsoft Basic Keywords and addresses, Willem L. van Pelt
28 Aanpassen regelbreeddte via het toetsenbord, Frans SMeehuyzen
47 Extended AIM Basic Junior patch on Basic program compressor
4 Tips & Trics, Wout van Dinther en Gerard van Roekel
29 Junior Command Characters, Coen Kleipool
34 Basicode-2 voor de Junior met SYM-Basic, Fridus Jonkman
36 Hexdump voor de Senior Monitor voo Junior met PROTON’s monitor, Rob Banen
44 UART schakeling voor Junior, A.A. Zwart
44 Textfiles with Junior, Camiel de Ly

De 6502 KENNER 33 – Augustus 1984

3 Epson FX80 printer routine for Junior with OS65D
8 Junior disassembler voor hexdisplay, Fridus Jonkman
17 Low cost Elekterminal Expansion, R. Baarslag
24 Spiraal, grafisch op Junior met VDU kaart, Japp van Toledo
33 Tracer en single step, voortzetting uitbreidingen SYM Basic op Junior, Frans Smeehuyzen

De 6502 KENNER 34 – Oktober 1984

36 Save en load routines PROTON DOS SYM-1 Basic op Junior, Frans Smeehuyzen
33 HEX ascii dump, FORTH Gert Klein
39 Wallbreaker for Junior with OHIO-DOS, Willem Kuitens
42 Maanlander, Maarten van Hintum
44 Junior 8K of Junior 64K, Hans Mooi

De 6502 KENNER 35 – December 1984

5 Junior met VDU kaart Greedy spelprogramma deel 1, Phons Bloemen
48 Junior met D.O.S, Koen van Nieuwenhove Speed

De 6502 KENNER 36 – Februari 1985

5 Junior met VDU kaart Het grafisch display, J.J.A. en J.A.J. Janssen
21 FORTH op Junior deel 1, Gert van Opbroek
24 OHIO DOS V3.3 Aanpassen I/O routines, Wout van Dinther
24 How to change the Memory Map of your FORTH system on Junior

De 6502 KENNER 37 – April 1985

17 Junior met DOSV2.0A Bug in Disc patches on ASSM/Ted, Hans buurman
45 FORTH op Junior computer, Gert van Opbroek

De 6502 KENNER 38 – Juni 1985

11 Dubbele dobbelsteen Junior met PM Maarten Lamey
22 ID en KB-9 Microsoft Programs, Camiel de Ly
23 VIA ACIA print, M.A. van der Laan
32 Patches op PM Junior
40 Sorting subroutine Junior Fernando Lopez

De 6502 KENNER 39 – Augustus 1985

10 DOS65 JUNIOR, another DOS for the Junior, Coen Kleipool
12 Boekbespreking
13 Time of day, de 6526 nader bekeken, Ruud H. Uphoff
18 Vraag en aanbod
19 Junior met OS65D V3.3 Uitbreidingen, Gert Klein
33 Junior Tape I/O, A.W. den Hertog
35 Ervaringen met de PC-2 computer van Proton Electronics
35 HCC Computerdagen 16/17 nov 1985 reductiebon
36 Tokenized Microsoft Basic Keywords and addresses CBM40XX, CBM 80XX, Nico de Vries
46 Automatische dataregel teller
47 FORTH op Junior deel 3, Gert van Opbroek

De 6502 KENNER 40 -Oktober 1985

39 Junior in Apple, Frans Verberkt
42 C64JUN, Junior leest C64 tapes, R.A.F. Bens

De 6502 KENNER 41 – December 1985

6 Basic teksteditor OHIO DOS Junior, Maarten van Hitum
15 Screen editor V3.0 SCRED 3.0 Junior met VDU kaart voor Basic of Comal, B. de Bruine

De 6502 KENNER 42 – Februari 1986

9 Real-time clock voor de Junior, Clock IC MC146818, M.J. Stiphorst
15 Octopus 65, fout in publicatie FCU kaart Elektuur Special
24 Octopus 65 Let it be, Will Cuypers
26 GRAF V2.4 Routines grafische kaart, J.J. A. JAnssen
38 Basic programma Competitiestanden Handbal Elektuur Junior deel 1, Gerard Keet

De 6502 KENNER 43 – April 1986

16 65(C)02 Vervanging 6502 in Junior, Jan Vernimmen
17 Elektor’s octopus diskettes available
18 Basic competitie standen deel 2, Gerard Keet
23 Een wait ingang voor de Junior, Roger Langeveld
29 Octopus Diskette copier version 2.2, Wolfgang Tietsch
44 Bankswitching for the Junior, Fernando Lopez

De 6502 KENNER 44 – Juni 1986

1 Inhoudsopgave
2 Alternatieve Break routine tbv CPU kaart, Frans Smeehuyzem
4 Elektor’s OCTOPUS/EC65 computer: A data buffer as afterthought, R.T. Overakker
6 Problem with EC65 poweron reset, Siegfried Losensky
7 Elektor’s Octopus/EC65 Modified diskette copier version 2.2 part 2
18 Junior interface card en gewijzigde VDU card, Pieter de Visser
21 Junior POSVAL Chessmonitor for Elektor with hexdisplay, Frans Raaijmakers
21 EC65 Patch realtime clock
29 Printer initialisation for EC65, Leif Rasmussen
29 EC65 SAMSON tips, Leif Rasmussen
31 Basic competitiestanden part 3, printroutine voor teletype 110 baud
38 Junior with Proton’s Senior monitor modified format lister, Rob Banen
45 6845 geprogrammeerd
48 Delete character routines tbv de Elektor VDU card

De 6502 KENNER 45 – Augustus 1986

3 Elektors EC65 Starcatcher Basic game
42 Junior with VDU OHIO DOS NUMBERS routines to handle input of numbers from the keyboard
12 Realtime clock 146818 IC routines, Frenando Lopez
21 Elektor VDU card modification, J.C. Rix
22 New Centronic routine for Junior/Octopus 65, Coen Boltjes
25 Junior POSVAL Chessmonitor for Elektor with hexdisplay, Frans Raaijmakers
43 Basic competitie standen deel 4, Gerard Keet
46 Use of cursor control keys ED, Rene Hettfleisch
46 Octopus/EC65 disks

De 6502 KENNER nr 46 – october 1986

5 Block graphics on EC65: screendump, Leif Rasmussen
6 An interrupt decoder for the 6809, Andrew Gregory
8 8K RAM voor de Atom, Karel Odon
8 Patch on Dr Tietsch’s copier program, Marc Lacheart
9 A macro loader and Saver for ED DOS65, Bram de Bruine
11 Bitpatroon voorde C64, Gerard van Roekel
11 TIP: 0 in data regels plaatsen, Gerard van Roekel
12 Basicprogrammas’ combineren 2 en 3 letterwoorden, Gert Kwetters, Bart van Pelt
13 Junior bekent kleur, Phons Bloemen
17 Look at real contents Atari, Henk Speksnijder
17 Modification VDU card Octopus65, Albert v.d. Beukel18 Junior POSVAL schaakmonitor part3 end, Frans Raaijmakers
18 Junior Changing the 6502 by a 65C02. Jan Vernimmen
19 Troubles with Micro Ade and Elektor’s Octopus, Marc Lacheart
19 Solution of Micro Ade problem of contineous erros, Ronald Hermans
20 Junior malfunction Display, Ronald Hermens
21 Directory Disk1 ‘System Loys diskette’, Fernando Lopez
22 Bell routine for Octopus/EC65 with Basicode interface card, Coen Boltjes
22 Junior POSVAL wijizigingen in gepubliceerde listing, Frans Raaijmakers
23 Error messages Junior, adapted for Junior, Ronald Hermens
25 PL3/4 straps poblem CPU card, Frans Smeehuijzen
30 Patch in the Octopus/EC65 standard monitor, Marc Lacheart
30 Patches on Disk 5A (Original OSI V3.3) Marc Lacheart
31 Problemen met de Octopus65 met RS232 printer, J.A. van Eken

De 6502 KENNER nr 47 – December 1987

4 Hardware adjustment Junior/Octopus with VDU card for use as a videotext terminel Prestel standard, Coen Boltjes
6 How to adjust the character generator for Videotex, Coen Boltjes
8 Junior Break key with serial keyboard, Gerard van Woerkom
12 Directory Disk 5a Ohio DOS
12 Junior dubbel adressering, Frans Bens
18 Tips and tricks for the EC65K/Junior, Coen Boltjes
19 MON65 op Junior, Erik v.d. Broek
20 The Junior Computer revisited, Fernando Lopes
28 Bell for EC65, Rasmussen and Lindstroem
32 Extension of OS-65D V3.3 with DEL command
38 Screen flickering, Andrew Gregory
38 Slave: bootstrap loader Junior, Ronald Hermens
39 TELEX programma MCB 1984, Marcel Breukink
44 Columns print for printing in two columns, Octopus, Leif Rasmussen
45 Hardcopy routine for Octopus, Coen Boltjes

De 6502 KENNER nr 48 – February 1987

5 Videotex program for the Junior Octopus, Coen Boltjes
26 Ascii dump with OS65D extended monitor, Gerrit van Woerkom
28 Working with Micro Ade and bankswitching on the Junior Computer, Fernando Lopes

De 6502 KENNER nr 49 – April 1987

7 EC65/Octopus Screendump for Kolorator, Leif rasmussen
11 Plotpoints Atari 520ST, Jan Vernimmen
16 Expansion for Ohio DOS Extensions, Coen Boltjes
25 EC65/Octopus How to get more memory space, Peter Linstrom
29 DOS65 ACIA 65C51 and modems. Bram de Bruine
31 Centronics input for DOS65 or Junior computer, Ernst Elderenbosch
32 How to modify the Elektor 64K memory card for use with DOS65, Andrew Gregory
33 Hoe wordt de video controller 6845 geprogrammeerd
39 Forth on the Junior, Frans Bakx
43 Maanlander Junior, Fridus Jonkman
46 Printer routine for Junior, Alfons v.d. Meutter

De 6502 KENNER – nr 50, Juni 1987

4 Fast alternative for the slow Junior cassette interface and software, Hans Christen
8 Solved problems Octopus vdu card monitor EPROM
19 Relocator for DOS Junior and Octopus 65, Coen Boltjes
21 RAM Test program for the Octopus 65, Marc Lacheart
36 Paperware service EPROM programmer for Junior, Andrew Gregory

De 6502 KENNER nr 51 – Augustus 1987

9 EC65/Octopus cassette motor control and Bell hardware, Marc Lacheart
17 EC65/Octopus Wordprocessor V3.0 available, Leif Rasmussen
17 EC65/OctopusPatch on Dr. Tietsch Copier program, P. Lindstrom, Leif Rasmussen
17 Printer problems with the Octopus, Maarten den Hertog
21 Loys extra, how to bind the systemdisk utilities, Leif Rasmussen
28 Junior tape routines on DOS65, Ernst Elderenbosch
26 Octofate: Fate for the Octopus, Coen Boltjes
26 Octopus inputverwerking, A.P. Oerlemans

De 6502 KENNER nr 52 – October 1987

25 EC65 EPROM disk loader
27 EC65 EPROM disk directory
32 EC65 NUMINT basic
34 EC65 Language study help
37 Junior MAZE

De 6502 KENNER 53 – december 1987

30 EC65 Modified version of Elektor’s listing stopper

De 6502 KENNER 57 – Augustus 1988

34 DOS Errors in words EC65

De uPKenner 61 – April 1989

28 EC65K EPROMs programmeren

COMPUSER Volume 1 Nr 2 March 1988

16 Screen noise on Junior with VDU: synchronize CPU and VDU
17 A description of the DOS65 Disc format
24 Tape backup and restore utility OCTOPUS/EC65, Marc Lachaert
35 OHIO DOS V3.X special for Junior, Dirk Picke

COMPUSER Volume 1 Nr 5 March 1988
1 Fractals in assembler EC65 Leif Rasmussen

COMPUSER Volume 2 Nr 1 January 1989
14 Transfer OCTOPUS into a development system, Peter F. de Pauw
34 Read time and date EC65, Peter lindstrom
38 Junior DOS65 Erik vd Broek

Junior software

Monitor ROMs, binaries and sources

The Monitor was published as a hex dump as second article in the Junior publication, See it here.
Note that this 1K ROM was assembled for address $1C00, since the Junior maps that location also to $FC00, where a iK 6502 boot ROM has to be. Of course this means trouble when the memory decoding is enhanced and Elektor spent much text and hardware to solve this. The best solution is not to use the original ROM but use a binary assembled for upper memory.
Here you see where to change the addresses.

A collection of dumps of various ROMs from Juniors, expansion cards, EC65/Octopus. Not tested but may be useful.
PM. TM Monitor etc, 506, Mini EPROM 511(n)
VDU, Character, Micro Ade, SYM AIM BASIC EPROMer 6502 tracer, 244, Mini EPROM 51
EC 65 Octopus ROMs, dumped from CPU cards
– a bootstrap eprom (ESS515 download here, source in Paperware 2) able to load OS65D (V3.1 or 3.3)

The system software of the Junior is made up of several ROMS. The Monitor ROM is the base system in 1K in a 2708 EPROM on the main board.
The Interface board offered space for 2716 type of EPROMS and audio tape management. ROMs like the PM, TM and PME appeared. See the Junior Book 4 for more information.

If you want a reliable ROM for a Junior, build it from source. Available sources are:
PM TM PME sources
PM source
Monitor ROM source at $FC00
Monitor, for $1C00! by Bram Prosman
PM PM PME sources
Monitor sources in CW Moser format, and recombined for $FC00

Junior paperware 3 and 4 sources

You can assemble these sources with the assembler included in the archive or with one of these fine assemblers:
TASM Telemark assembler, runs on Windows 10.
A65 assembler, run in DOSBOX or VDOS.

Microsoft KB-9 Basic V1.1

How to adapt KB-9 BASIC to the Junior

KB-9 stands for Microsoft BASIC V1.1 for the KIM-1  with 9 digits precision. .
Scanned manual
The original KIM-1 KB9 Microsoft BASIC V1.1, binary and papertapeKB9 for Junior updated in BIN, hex dump and wave format
All the files here: archive with audio wave file, dump on terminal, binary and conversion software.
(See also Junior with KB9 and OS65DV3.3 – Retro Computing)

See the KIM-1 Software page for more information on KB-9 BASIC.

Tiny Basic

Tom Pitman’s Tiny basic. Small enough to fit in th 1K KIM-1, yet a real Basic interpreter

Tiny Basic binaries, low memory version and version with start address 2000
Tiny Basic manual as pdf
KIM Kenner 23 Tiny Basic, Filip van Kenhove, adapt to Elektor Junior

See the KIM-1 Software page for more information on Tiny Basic.


COMAL is an interpreted structured language. I have only as original the KIM User Club Elektor Junior version, and as with most of the 6502 SBC programs, not that difficult to adapt to a KIM-1, as shown in the last pages of the manual (in/out/break character, load/save tape, memory layout).
KGN COMAL binary
Manual KGN COMAL (dutch)

See the KIM-1 Software page for more information on Comal.


Various sources

CW sources
Junior hypertape test
Junior hypertape
Junior sym basic basicode source read write part 1
Junior sym basic basicode source read write part 2
RTTY sources
RTTY sources
Tutor Morse code KIM Kenner
Elektuur issue 222 clock source

Junior tapes

In a package with Elektor hardware Octopus cards I once bought, I found a little book and a floppy disk in DOS65 format with Junior tape dumps. Already in binary format, made with what I think is an 68000/Atari/Amiga program. Source is also included. Download here the archive

Included are sources and programs like
– Junior PM and TM
– memory test
– Micro Ade, KIM-1 and Junior version, also in source format and extended format
– Clock source program
– CW Moser assembler/editor, also in source
– Forth, Comal
– SYM Basic adapted to Junior

See the included juniortapes.txt for a complete listing of what is included on tape. Note that most files have been ‘unpacked’ and renamed and are available here and on the KIM-1 Software page , either as binary or as source. See the PC Utilities page how to extract the assembler source files.

Junior DOS

The floppy disk system for the Junior was based upon OS-65 V3D from Ohio Scientific, the interface is a clone and, since the software was for sale, a separate object.


The steps described by Elektor in the articles with some modern additions.
A Junior able to run OS65DV3.3 needs an expansion card,  a RAM card (his is 64K) and the Elektor floppy controller, which is identical to the OSI one (6850 + 6820 ICs)

Instead of a real floppy drive one can use the  hardware Gotek floppy emulator with the Flashfloppy firmware. And used the manuals images of, and the OSIHFE utility described in the OSI Web forum posts.

Elektor made a bootstrap eprom (ESS515 download here, source in Paperware 2) able to
* load OS65D (V3.1 or 3.3 as far as I know) from floppy
* give basic I/O capability (RS232 and floppy)
* manage hex display and keyboard
* modify OS65 for the hex display after the very first load to fully adapt them to the system ( about 10 bytes to modify)

PMV for OS65D source checked by Philippe Roehr
See also Junior with KB9 and OS65DV3.3 the work done by Philipee Roehr