KIM 6530 replacement

Have a KIM-1 with faulty 6530? Look here for replacement with 6532 and some.


KIM-1 6530 Replacement

Text, copyright and product by Corsham Technologies

If you don’t want to build your own version from schematics, Corsham Tech does offer three options:

  • Bare Board
  • Kit
  • Assembled

The bare board is just the board.  Documentation is on this page.  It’s mailed in a small envelope and can be built with commonly available part

Like many people, I (Bob, Corsham Tech) have a KIM-1 in my collection with a dead 6530 chip.  Fortunately mine wasn’t too bad, but one of the I/O pins didn’t work so the display always had one segment lit and the TTY port would not work.  After many hours of searching for a way to replace this one defective chip with an equivalent circuit, it became apparent a lot of people were trying to do the same thing, some claiming to have a solution, some not, but no schematics ever appeared.  Without schematics, there is no solution.

Rather than letting others go through all the effort to reverse engineer the 6530, I decided to make my own, and to publish the schematic.  This work was heavily taken from Ruud’s excellent tutorial on his efforts to replace a 6530 in a Commodore disk drive.  Please go to his page for an explanation: or see the 6530 pages here.

Since the 6530-002 and 6530-003 in the KIM have different mapping of ports, his exact schematic is not right for the KIM, so I borrowed some of his KIM-1 clone ideas and designed my board from it.


  • No, the schematic is not pretty.  I can spend some time and shuffle parts around to make the parts placement neater, but if you’re contemplating building this, I’m sure you’ll have no problems following the schematic.
  • Pin usage has not been optimized.  This was breadboarded but the PC board design is not done so some of the pins on the 74LS00 might change.
  • There are three jumpers with U2 and 003.  The intent was to be able to replace either of the two 6530s on the KIM and both U2 and U3 have been tested.
  • A 28C64 EPROM was chosen because (A) they’re readily available, (B) common USB programmers can program them, and (C) the offset in an Intel HEX file for the KIM PROMs will be at the proper offset when you load the files into your programmer’s memory.  Ie, the 002 device’s offset at 1C00 will be at offset 1C00 in the EEPROM.


PDF version of the manual.

EEPROM Contents

The basic KIM has an 8K memory map so using an 8K EPROM/EEPROM makes things easier because the address in the HEX file is exactly the right offset into the EPROM.  If you don’t understand this, don’t worry, you don’t need to.

I deleted the two individual hex files and replaced it with a single file that covers both halves of the KIM PROM:


The image is a raw dump from a working KIM, not re-assembled from source.  Note that I had to add an extension of txt so that WordPress would allow me to upload them, but take off that extension when you save them to your computer.

Design Files

Bare boards are available, but these are the files you can use to generate your own. First, this is the GERBER file from the revision 1 boards I sent to have boards produced. If you want to make your own boards without any modifications then just upload this file to your favorite PC board manufacturer and they can give you a quote:


If you use the EAGLE CAD package, here are the files needed for the project. This has the epf, brd and sch files:


BTW, this is what the top layer of the board looks like, minus any traces:

Just like Ruud’s original design, this has the 6530 header and 6532 socket overlapping each other. For the header that is soldered to the underside of the PC board and plugs into the KIM, I suggest a header with narrow pins. I used CNC Tech part number 220-1-40-006, available from Digikey as part number 1175-1527-5-ND. Be aware that the cross-pieces of the IC socket and the header will block the pins for the other, so you’ll need to cut them from either the socket or the header (whichever you solder last).

VERY IMPORTANT: Notice that IC3 and IC5 are polarized exactly opposite from the others! When you insert sockets and chips, double-check you’ve got them oriented in the right direction!

Prototype in action!

Replacement board in U3 location, works!


TIM 1 System by Joseph Watson

In the Facebook group ‘6502 programming’ Joseph Waton published a story about his TIM 1 system and photos.



VAE T4 system

The dutch company Visser Assembling Electronics, Alkmaar, working for and in cooperation with the dutch carpet-factory Forbo Krommenie, developed a system based upon the KIM-1.
The T4 system consist of a large portfiolio of RAM, ROM, EPROM, input (Analog and Digital) and Output boards. Also a videoram card was developed.

Scanned documentation and all photos of the system





Radio Bulletin

The dutch magazine Radio Bulletin (RB, RB Electronics) has a long history, going way back to the early years of electronics. The name was derived from what electronics meant for amateurs in these days: building radios yourself.
It was published by Uitgeverij de Muiderkring, a publishing company in the Amroh group of companies.

The magazine was published in large volumes in the years 1970-1985, due to the popularity of do-it-yourself electronics and audio. Also the beginning of the microprocessor revolution was adequately covered and the great years of the hobbycomputers 1980-1990 were contributing to the success. Besides the magazine Uitgeverij de Muiderkring published many books on electronics. After 1990 the success faded and the magazine left the mass market and stopped in 2003. The publishing company Uitgeverij de Muiderkring, together with Amroh, went bankrupt in 2002 (I lived closely to the last location and saw the empty offices when passing by).

In 1977 Dick de Boer joined the staff of RB and introduced the readers to microprocessors and in particular the 6502 and the KIM-1. Also the KIM Gebruikers Club and the HCC were founded that year and RB started to write articles about all this exciting new developments!
I was then already a freelance writer about electronics but Dick made me study the microcomputer such as the KIM-1 and made me join the KIM
Gebruikers Club and the HCC (member 760 member). Dick de Boer, his successor Paul de Beer and me (Hans Otten) and others wrote many articles about the KIM-1 and related 6502 based systems for Radio Bulletin. Especially Dick wrote good introduction articles and developed sophisticated hardware and software like a graphical display. After leaving the magazine he became a software engineer and helped me also to my first job as software engineer in 1980. Me and Paul de Beer concentrated more on expanding 6502 systems like the KIM-1 with memory (RAM, ROM) and I/O cards like PIA, VIA and ACIA and mass-storage such as the Mini Digital Cassette Recorder. The bus of this expansion system was the so called BEM-bus.

I did translate a book Computer Interfaces by Owen Bishop for de Muiderkring to dutch. A scanned version is presented here.

All these articles are downloadable here, as they describe my publishing history and my KIM-1 system, designs by us of which the prints sold quite well. As you can see in the long list of articles the KIM and the 6502 played a major role in the microprocessor revolution starting in 1977 and lasting until 1987 for me.

What you see about Amroh, Uitgeverij de Muiderkring and Radio Bulletin is:

Selection of my and others articles 1977 – 1987 in Radio Bulletin
the RB Specials
the Cosmicos 1802 CPU based system by H.B. Stuurman, book and articles
some bits about the long history of Radio Bulletin
Elektronica ABC, the diy magazine

See also:

– Dr Blan articles on Step-by-Step radios
– Step by Step radio by Amroh



Developed by Mos Technology. later acquired by Commodore, to show the possibilities of the 6502 microprocessor but quickly discovered as the first mass-produced personal computer. Easy to extend, lots of detailed documentation. With assembler/editors, first Microsoft Basic on cassette and even a Pascal compiler, it could do a lot. The first have an original Mos Technology logo, later versions have the Commodore logo on the board, small technical differences other than more recent 6502 IC’s without the infamous ROR bug.
This prehistoric computer has no “real” keyboard and no video output, program are entered by the small hexadecimal keyboard (located in the lower right part of the picture) and results are displayed on the small LED “screen” (it can display only 6 digits). It has a simple monitor that allows one to examine & modify memory, load and save paper tape, load and save cassette tape, run and debug programs through a ‘single step’ mode. The monitor works with the built in keypad and LEDs, or a terminal like the Teletype ASR33. This 20 mA current loop is easy to adapt to RS232C and so any videoterminal can be used.

Information on the KIM-1, also reachable from the menu on the right:

Prototype KIM-1

On team6502  I found a photo of a prototype KIM-1 at MOS Technology, Terry Holdt has this in his office.
The layout is different from the final product, everything seems to be present on this prototype.