The C128Neo is a project to create new mainboards for the Commodore 128 computer. The foundation is a reverse engineering of the revision 9 mainboard and then schematic and PCB layout capture using KiCad.
Latest blog entries
BOM and early boards
21 January 2020
Bill of materials Hi all. The first revision of the bill of materials have been uploaded. The link can also be found in the menu and on the assembly guide page. Some components can be a bit tricky to source unfortunately.
Early bird boards I also have three spare revision 3 boards still for sale. They are fully functional electrically and mechanically but do have some minor cosmetic issues like a misplaced silkscreen text and similar things.
Fixes: VDC R/W
13 January 2020
Continuing with the series on fixes compared to the original Commodore PCB, we now come to these two wires:
(Ignore the capacitor, that’s a different story)
If we look closely, we can see that one pin on the VDC has been isolated from the PCB traces by drilling them out in two places. Then new wires have been pulled to connect the now isolated pin on the VDC somewhere and another wire was used to bypass that segment for the original trace.
12 January 2020
This week I received the revision 3 boards I had ordered.
I promptly set about assembling one for testing. I’ve finally managed to sort out some of the mechanical sizing issues I’ve been having with some of the components, in this particular case the RF modulator and the RF cage around the video chips which now fit as they should.
All worked as it should after assembly and I only noted some minor cosmetic issues to be resolved.
05 January 2020
So, I figured I would make a small series of posts on the various little fixes that has been implemented on the C128 Neo boards. First up is this little fellow that is manually soldered to the underside of the PCB close to the 8502 CPU.
Since there are no markings I ended up following traces around to figure out what it is for. In the commodore schematic it is marked as R102 and sits between the 1MHZ and D1MHZ lines.
Revision 2 PCBs
18 December 2019
I received the revision 2 boards from the PCB shop last week and spent some time soldering one together. I went with green solder mask this time just to see how it would look when closer to the original colours, turns out not too bad. I prefer the red colour though so I think the boards I make will be red in the future.
Quite a few improvements since rev.
PCB preparation work
08 December 2019
Doing PCB layout for something as large as the C128 board is not an easy task, shown by the comment above that can be found on the original C128 boards. As such, I made the decision early on to not make any major changes, just follow the original design as closely as feasible. To help with this process, some steps are involved. I started with buying a spare board from eBay that could be sacrificed.
The history behind the C128Neo
30 November 2019
I received my first own computer on my tenth birthday, a shiny brand new Commdore 128. As most kids in the 80s I then spend hours and days playing games and enjoying myself. Over time however I started getting interested all the other things that were mentioned in the manual that came with the system. This was the start of my career working in IT so you could fairly reasonably state that the C128 hand book has been in some ways the most influential book in my life.
Introducing the C128 Neo
27 November 2019
The C128Neo is a reverse engineered reproduction of the Commodore 128 computer PCB.
The only changes made have been minimal changes to make it easier to assemble and use, while not changing the functionality. The intention is to be used as a replacement board for computers where the factory board has gone beyond feasible repair.
The picture above is a first revision board, which was put together in order to verify the functionality of the layout and also to iron out any issues with the mechanical design.