This self-build kit is a superb way to get involved at some fundamental computer engineering.

The Z80 is an excellent choice for a ‘home-brew’ computer: single 5v supply, all the control/state inputs/outputs you’d need to distinguish instruction from data accesses, separate IO addressing, great interrupt options and even dynamic memory refresh capabilities.

The modular design approach adopted in the RC2014 design is well delivered. Separate CPU, system clock generator, ROM (with MS BASIC abs monitor), RAM and Serial IO modules gives you an excellent base system, which with a suitable interface to a PC or a MAC (either used as a terminal display) gets you up-and-running pretty quickly, once you’ve completed building the motherboard and modules.

What I really like about the RC2014 is that it’s open: anyone can devise and build a new module - that flexibility is really welcome as it allows the RC2014 to be used in a myriad of applications.

Given this kit has a reasonable, not full, level of documentation, ‘newbies’ to electronics, the soldering iron etc may be put off but there is some excellent unofficial support available, driven by friendly, enthusiastic and knowledgeable interest group/forum members.

Adventures in RC2014 kit assembly
10/4/2019 – Rev 1.0
Greg Peterson

I recently stumbled across the RC2014 retro computer based on the Z80 microprocessor on the Tindie website. Having grown up in the early days of personal computing, this inexpensive computer system looked like a fun project, so I ordered one.

Potential purchasers should know a few things I rapidly learned about this kit. I ordered the “Pro” version of the kit. Documentation exists, but is scattered across the web necessitating some hunting. Print out the pictures for your kit as you find them on the web, as well as the schematics, you will need them. There appears to be at least 3 versions of this kit available, and the boards differ, so your boards may or may not match the web pics you find, or the boards I received.

I would not call this kit suitable for a beginner. The documentation is scattered and presumes a fair knowledge of eight bit retro computer system design. The actually assembly in not overly arduous, though the boards are small. My system went together in three nights, which included correcting my pin installation mistake on my CPU board.

You will need a quality, fine tip soldering iron, preferably with temperature control. I purchased mine from Circuit Specialists on the web. Don’t you dare try to assemble the kit with a soldering gun. You will also need a small pair of edge cutters and a small pair of needle nose pliers. You will also need some very small diameter rosin core solder (try EBAY). If you have a PCB tool to hold the board, it will make assembly easier, but is not required. You might also like to buy a small quantity of single and double row right angle pin headers on EBAY. As I age, my eyesight is declining. There was a time I could read the part number on a tunnel diode, but no longer. I have purchased a small Chinese video microscope on EBAY. No eyepieces to look through, the image is displayed on an LCD screen. This has greatly helped me with the close work, especially looking for un-intended solder bridges. One final helpful tool is an IC pin straightener. This little double-sided plastic tool will drastically reduce the number of bent pins encountered when inserting chips into sockets. It will also relieve you from the “bending IC pins against a table edge” trick.

My kit arrived quite rapidly, considering it shipped from England. It comes in a remarkably small package. The PC boards are all of high quality, as are the components.

I suggest you unpack your kit by board type. My kit contained boards for a backplane, Clock generator, Z80 CPU, ROM, RAM, Serial and Compact flash with CP/M loaded. Also in ROM is Microsoft BASIC, RomWBW, and SCM (Small Computer Monitor). My kit came with a loose collection of parts, and several individually packaged boards with parts. Many of the web pictures show a board with its associated parts arrayed around it. I suggest you try to emulate the pictures with the parts you have.

The female pin connector on the backplane has 40 receptacles for pins. The right angle edge connectors on the board have 40 pins, but only 39 matching mounting holes on the board. So you wind up with one pin hanging off the end of the board. I left this pin on my boards to minimize the possibility of inserting a board one pin off.

Nobody seems to want to tell you what a minimal system consists of. I assume the Compact flash with CP/M is not needed initially. You will need a CPU, Clock generator, Serial board, ROM and RAM.

Nobody seems to want to tell you how to jumper your boards. The pictures will come in very handy. Being able to read a schematic will be an asset as well. I am assuming the shown jumper positions in the board pictures will result in a properly running system, but I don’t know this (yet).

A quick inspection of the boards reveals some have holes for a double row of edge connector pins for the extended RC2014 bus, and some have only a single row of pins. This resulted in my first mistake assembling the kit. Do not mix single row and double row edge connector pins. The proper assembly method for boards with double rows of edge connector pins is to to use the double row pin strips and to remove un-needed pins. A pin is un-needed if there is no corresponding mounting hole in the board. A small pair of needle nose pliers will allow you to grasp pins and, giving a small twist to the pin, pull it free from the black plastic strip. Exercise due care when pulling the pin lest you break the black plastic holder. The pictures do not show this very well. If you do this wrong, you will get to un-solder the mis-installed pins and remove them, possibly damaging your board(s), depending upon your soldering skills.

A hint here, if you assemble the motherboard after installing the edge connector pins on the boards, you can use a female backplane connector to help hold the flexible pin strip straight during board assembly.

Another hint, when installing IC sockets, tack diagonal opposite corners of the socket down with solder. Then, while pressing gently on the socket, reflow the solder on the tacked pins to insure the socket seats directly against the board.

The person that did the PCB layout left little room to bend resistor leads down to fit the PCB holes. You will pretty much have to bend the resistor leads directly down with no radius. So how hard would it have been to leave 1/8 inch on each end of the resistors? Other than this tight spacing, I have nothing to quibble about with the boards. Speaking to quality workmanship, do orient your resistors the same. I prefer to read the color code left to right or top to bottom. It just looks sloppy otherwise.

Some serial board documentation mentions a 68B50 UART. Matching a Motorola serial chip to an Intel/Zilog chip bus seems strange to me. My kit came with a Zilog SIO/2 UART, not the 68B50. While using the RS-232 serial protocol, my board came with no level translator to match the +/- voltage levels of the spec. Something like a MAX232 interface chip is what I expected, but there is no provision for this. Instead an FTDI TTL to USB cable is suggested. Of course, the pictures do not show this cable installed on a serial board. The cable can be installed on the pins with two orientations. Close inspection of the board clearly shows pin 1 labeled ground. My cable has a blue wire in this position on the cable connector, or, flipping the connector over, a red wire. I have no key or marking to ID pin one on the connector, but I have developed a natural aversion to hooking red wires to ground, and have not resolved this yet.

Then too, there is the 5 volt 3 Volt controversy. My serial board will be putting out 5 Volts, retro parts run at 5 Volts. I have no idea what my FTDI cable expects, but if it wants 3 Volts, nothing good will result from connecting the two together. A bit of multimeter sleuthing should shed some light on things.

There is an FTDI cable spec on the web, but the cable seems to be loosely defined to me. My spec has no green wire, but my cable does, so I really don’t know what signal this wire supports. My cable has six positions, and my header on the board has six pins, but some connector diagrams support more connections.

The Pageable ROM card has a set of pads underneath IC U2, a 74HCT138. This chip is a decoder, so it would seem logical that these pads set the I/O address of the card. Of course, nobody tells you what that address should be, or how to jumper the pads to achieve it. I am sure that the software has some definite assumptions about where things are located. So the exploratory path is to consult the schematic and perhaps chase the software assumptions back through the source listings, which are available on the web. Of course, you do have to find the listing that corresponds to the contents of the ROM you have.

I would like to figure out how to duplicate the compact flash module. I would feel much safer if I had a duplicate, lest I damage it. I tried plugging it in to a Compact Flash adapter on my PC, but no dice. Windows 7 does not speak CP/M File structures.

My RC2014 adventure continues. I have serial interface issues, and jumper issues to work through, but problem solving is part of the fun, isn't it.

It went together quickly, without problem. had com running after about an hour. Thanks for creating a great set of kits.
Order number ending in 626

The kit comes with clear instructions and all the parts needed to build a working computer. Build itself took only a few hours and the machine booted after a few tries - make sure to pay attention to jumper settings! You also get a brief but useful troubleshooting section that covered the mistakes I initially made.

Communication with the author of the kit was excellent - I got a quick and professional reply.

Two small downsides: the modules aren't all oriented the same way, so I ended up with two modules facing "left" when plugged in and two modules facing "right". This can be avoided by switching the header to the other side of the board, but that means de-soldering 80 connections. Also, while the laser-cut case is very well made and comes together nicely, it didn't come with printed instructions for assembly - it goes together logically, but I was initially confused about the power LED ending up underneath the top panel, or the function of the cardboard insert (don't throw it out!).

Both of those are minor nitpicks and neither stops me from wholeheartedly recommending this kit. It's fun, it's educational and it's a solid basis for expansion.

I didn't rate the documentation as highly as it didn't come with any, but it is fairly obvious how to put together.

It came with a replacement button which has a longer button part so you can press it when the enclosure is on. If you're like me and nervous about unsoldering and resoldering things and plan on getting an enclosure, perhaps buy the enclosure at the same time so you can put the button on when you first assemble.

It's a very tight fit, which is good, but just be aware in case you put things on crooked.

It looks good. I got the Poplar one.