Cloning circuit boards for antique computers?

Question

Would it be feasible to create direct clones of obsolete and increasingly hard-to-find motherboards and controller boards for vintage computers?

Most of the early 1980s technology was either single side or double sided printed circuit boards, so apparently a direct clone should be possible by simply:

• Making note of all component values and finding modern equivalents
• Reading the ROM images and making copies onto new chips
• Desoldering and removing all chips and components
• Photographing the board and doing some image editing to create new copper etch, drill, and label masks

As out-of-production but highly-desired hardware becomes increasingly more rare and expensive, such as accelerator cards for antique systems, this may be the only way to make more available for potential users.

Disregarding issues of licensing and copyright for obsolete ROMs and mask designs from companies that either don't exist anymore or no longer care about the old hardware, is this feasible, and is anyone already doing this?

Answer 1

What you describe would be a possible way of replicating a vintage computer. The approach does, however, have some flaws that make it unlikely (or undesirable) to go this route, at least for designs newer than about mid-eighties - And it maybe is a solution for a problem that doesn't really exist:

• You need to find someone to donate the victim for the dissection. The more worthy of replication the board is, the less likely you'll find a donor. Be aware there is a fair chance of the victim not surviving this exercise. Quite some of vintage computer PCBs weren't of the best quality when new, and the decades didn't help that much. Some PCB makes are known to dissolve their traces as early as being in sight of a hot soldering iron.
• A lot of vintage computers, especially home computers, used custom chips to minimise production cost. With the upcome of ASIC and PLA technology in the eighties, most of the computer manufacturers jumped on this technology as it offered ways to radically simplify a computer or create unique technology opportunities - Those custom chips will today most likely be just as rare as the original motherboards. And once you find one, it is very likely to come with a working board - so, why replace something that is still working?
• Because of the above, creating a new computer from old is, at least in a lot of cases, simply scavenging historical material. And the PCB itself is one of the most unlikely things to break in a vintage computer - Why replace something that isn't broke?
• Even some of the non-custom chips of the vintage computer are very likely no longer be available as new stock (Like nearly all of the Motorola 68k series or most of the 80ies exotic dynamic RAM chips). Most of them can be replaced with modern counterparts, but that will very likely require re-working the PCB. So why copy an old PCB if it needs re-work anyhow?
• Even if you manage to create a 100% replica, to be able to do at least something minimally useful with you replica, you should be able to interface with modern equipment. This most probably also requires re-work of the vintage PCB. Some ways of working, like handling audio tape for storage, is just too clumsy when there are modern replacements.
• And, to be honest: vintage computer schematics are normally not that complicated to not be able to recreate them by just tracing the PCB manually or using historical documentation as a starting point. Using modern PCB layout and manufacturing technology, re-creating the board is not the most complicated part in creating a working computer. The challenges lie mainly in the custom or otherwise no longer available chips and in the ways how you interface to modern storage technology without giving up compatibility to "the original thing".

100% replicas of vintage (80ies) computers are thus not very likely to see the light of day, at least for designs where some or all of the above applies.

An example from the ZX Spectrum world: here follow two alternative examples of feasible mixed approaches to re-creating that computer in "pure, vintage" hardware:

1. "Just Speccy" is a recreated ZX Spectrum 128 based on the original computer. It does, however, have a heavily re-worked PCB being able to use modern components for memory and external storage, and uses an original ZX Spectrum ULA. Still, it suffers from increasing non-availability of these original vintage ZX Spectrum 128 ULAs, custom chips that can only be scavenged from old ZX Spectrums.
2. The "Harlequin" is a modern recreated Spectrum that uses (still somewhat vintage, but still available) TTL technology to recreate a ZX Spectrum computer without using vintage custom chips (except the Z80 CPU, which can still be bought in quantities) - The ZX Spectrum ULA is entirely re-engineered here in TTL logic. This is very much more effort, but has the advantage of not being reliant on draining ULA chip supply. Obviously, the PCB of the Harlequin doesn't really resemble much similarity with the original ZX Spectrum.

Even if the examples above both create a nearly 100% compatible ZX Spectrum re-make, their PCBs don't resemble much closeness to the original ZX Spectrum 128 computer. Approaches like the above are much more feasible than 100% replicas.

Answer 2

Circuit Boards

• Mimeo 1 is a replica of the Apple I motherboard.
• Rev 0 Replica is a replica of the Apple II Revision 0 motherboard.
• A replica of the Amiga 500 Rev 8 motherboard.

Chips

• Individual Computers SuperPLA V3 is a plug-in replacement for Commodore 64's PLA chips that often go bad.
• GGLabs F2R16 is a flash-memory-based plug-in replacement for 27C400 EPROMs that are no longer in production.

Other Components

• Remanufactured DB19 connectors

Answer 3

Based on actual projects that have been manufactured for the retrocomputing community, the tendency is toward enhancing the boards to take advantage of some modern components, rather than producing an exact clone.

There are several projects that have created replacement motherboards for retrocomputers from Apple and Commodore.

• replica 1 plus Apple I replica and Micro-KIM KIM 1 replica from Briel Computers
• C64 Reloaded and A1200 Reloaded (wip) from Individual Computers

In most cases, original chips and ROMs need to be supplied. A user that owns a legitimate ROM could provide the firmware themselves, or the manufacturer may elect to license the rights to distribute the firmware.

It seems that fixing common "issues" in the original, such as unreliable power supplies, unsupported peripheral connectors, and out-of-date firmware, RAM, and storage media, is easily addressed while creating a highly compatible, but not perfect clone, motherboard replacement.

Also, there are a number of projects that re-create the old chip functionality using FPGA devices, such as the MIST Project. While this would not be suitable for creating a replica of the original motherboard, it could be used as a motherboard replacement in the original case.

Answer 4

The short answer is yes.

Of course, the longer answer depends on what is the ultimate goal? is it to attempt to produce modern replicas with 100% new build parts (or using some percentage of original parts), or is it to attempt to remove the discrete components from a cracked/corroded original board, and replace the board itself, recycling the original parts? Perhaps all of the above?

Anything is possible. PCB manufacturers are cheap nowadays; I regularly get small boards produced out of China: $10 for 10 boards. My colleagues have had slightly higher quality boards produced out of Germany.

The main hurdle to what you are proposing, will be the schematic capture stage. Depending on the vintage of the boards you are copying, many older boards were laid out by hand and parts density is low. This would allow you to visually reverse engineer the schematic from the boards, draw it up in modern software and go from there. If the original boards are a bit more complex, you might need to trace out the original design with a multimeter/oscilloscope and perhaps simulate the resultant schematic in software to make sure it functions as it's meant to.

Another factor is the availability of the discrete parts; many parts are obsolete and discontinued these days, particularly peripheral driver chips. As mentioned in other posts, some parts were specific to the original computer manufacturer.

All things considered, you might wind up with a 1:1 replica, or something with modern components substituted in to preserve the original functionality. It is up to you to consider how 'authentic' such a board would be if you're attempting to sell them; many older oscilloscopes had the traces on the boards laid out by hand with tape, and part of the appeal is the look of these hand laid boards. An example of what I mean can be found on a NES control board, as seen here. So yes it is possible, but 'feasible' depends on your final goal, and how desirable what you're making will be to others if you intend to sell limited production replicas.

As a final note, although I haven't done anything as complicated/rare as an accelerator card, I have done something similar. The company I work for has several 80's vintage analogue front end amplifiers for data logging, many of which now have non-functional channels. I've copied the original schematic, updated the op-amps to more modern high-bandwidth versions and surface-mount versions of some of the parts and had them produced as updated replacements. I've also seen some projects online where people have gutted old game console cartridges, desoldered the eprom chips containing the original game code, and replaced the core chip with another one which has been programmed with a different game. At the time I saw this I considered the feasibility of producing new-build cartridge boards and emulating the CIC chip with something modern like an ARM chip. The idea came to nothing, but it's inline with what you're proposing.

Answer 5

Redesigning vintage motherboards can be a great thing. Anyone who's into this hobby (vintage/retro computers) know that the reason to do anything with this stuff isn't about money. But the love of the hobby.

Although, some people have certainly made money doing it.

Anyway, coming from a person who is designing his own motherboards for retro computers, I recommend to start small. One mistake is that not all 80's era motherboards were two layer boards.

Another thing to consider is that some of these computers were more complicated than people assume. For example, the Apple IIe did use some custom chips to reduce costs. The original Apple II was more off the shelf.

Both of them used DRAM that are hard to obtain these days. So between the DRAM and the custom chips, it would be a LOT of work to reproduce the Apple II line of motherboards.

However, it HAS been done.

Again, I would suggest starting small. If you really want to design something of that vintage, one great example is the Mockingboard sound card for the Apple II. I've built them on breadboards and they are still sought after.

Plus, you can find the schematics online. And, the chips are all very easy to obtain.

Once you get good at building peripheral cards, for example, then designing a complete motherboard would be easier.