Now that the Z80-MBC2 and uTerm are both up and running, it’s time to give it all a nice home. I went through several different ideas on how I wanted the final computer to look, from doing a full custom 3D printed case, to a small “all-in-one” keyboard style case like the Commodore VIC 20/64 “bread bin”, to something “boxier” to better fit 70’s era machines like the Altair, IMSAI, and SWTPC. The custom 3D printed case idea died very early on, I quickly realized I simply don’t have the time or skills to design and print a custom case that size, at least not yet. Perhaps I will revisit this idea in the future once I’ve honed my 3D design and printing skills further. The VIC 20/C64 style bread bin sounded great until I realized I couldn’t realistically find a case to fit my needs, in the size I wanted, at a reasonable price, and I had no desire to incorporate the keyboard into the final build. In the end I settled on a much more realistic and era appropriate “boxy” case that better represented machines of that era and the vision I had in my head. Also, this style of enclosure is much more readily available, inexpensive, and easy to modify.
Buy Case: https://amzn.to/3FD9XgF
I really wanted the final machine to look like a “next step” for these early CP/M machines, with proper front panel buttons and lights. As well the keyboard port on the front panel for ease of use. On the back panel I put the SD card, power, VGA output, and the transparent serial connection so you could still connect to the computer that way if necessary. The last thing I would like to do is extend the GPIO to the back so it could be easily accessed, but that’s something I will tackle later since I haven’t decided exactly how I want to accomplish that. I’ll likely use a simple pin header that can connect to an external break-out board via a ribbon cable.
Here are a few things to note that may influence your own design choices, as it did mine…
Once you have the system setup how you like it, you’ll find yourself swapping the SD card out much less often, perhaps on the rare occasion you want to add something else you may have come across or if there’s an update released by the original Z80-MBC2 author. So having external front or back panel access to it isn’t necessarily a must, especially if your case is easy to open. I put mine on back for that reason, and because it’s a micro-SD and wasn’t sure if I could make the slot look nice enough to be front facing. Full size SD cards are easier to work with and I hate when I have to use my fingernail or a tool to insert and remove the micro cards.
I put the keyboard port in the front instead of the back purely for convenience. My system won’t be setup in the same spot all the time, and will get moved around quite a bit, so it made more sense to put it on the front panel. Also, since that’s where the port is on the uTerm, it just made it easier for the internal layout. I also used a PS/2 to USB adapter for ease of use since a majority of USB keyboards will work fine with this computer.
The transparent serial connection went on the back simply because it won’t get much use, but it’s still nice to have. I also went with USB type B because I prefer it over all the other port types. It’s more robust than its smaller counterparts and type B cables are still cheap and very abundant. I could have just used a pin header but incorporating the serial USB into the design just made things easier for later, especially since I have a few of these lying around and can spare one for this build.
Designing the layout and look of the front and back panels took quite a bit of time to get done and went through several different re-designs as the build progressed and I better realized how much space I actually had to work with. Getting it to look like it belonged in the late 70’s or early 80’s, with a bit of modern flare, wasn’t nearly as easy as I had thought. Once I was happy with the design however, it was just a matter of printing it onto sheets of adhesive vinyl to attach to the panels. The panels themselves had two options, drill and cut out the holes on the included panels or printing my own. In the end I decided to print my own to give me more 3D design practice, and it guaranteed a good fit.
The inside layout was also a bit of a challenge, I wanted it as “clean” as possible, but I also had a very limited amount of space to work with. I had to extend everything to the front panel while trying to maintain the ability to easily disconnect everything if necessary. I thought about designing a custom front panel PCB, but I really didn’t want to wait for it to arrive and I wasn’t sure I could make it cleanly fit. So, I decided to just extend everything directly using pin headers. It makes it easy to replace anything that may go bad and it fits into the limited space. I also think it fits better with the overall aesthetic of the machine since many of these early home computers had a lot of DIY modifications.
Mounting the PCBs was accomplished using a custom 3D printed support structure that I designed to hold everything in place, but still allow for easy servicing should the need arise. The Z80-MBC2 and uTerm are both held in place using screws, and the SD card and RTC are held in place using 3M double sided mounting tape. The base of the support structure is screwed to the case, and the two upper sections are sitting on top of 6 removable 3D printed standoffs. It’s not perfect, but the overall design fits in the limited space, holds everything in place, is easy to disassemble, and it looks the part of a homebrew computer.
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| More photos coming soon! |
One of the reasons I wanted the Z80-MBC2 was to learn more on how these old machines worked, and since their so simple, they’re easy to learn on. I enjoy messing around with the old software and games, and it can actually still be useful, but that’s not the real point. Sometimes the best part of a trip is the journey, not the destination. Most people will look at old retro machines like this and think “what’s the point?”, and if you have to ask that question, then I’m not going to be able to explain it to you. That simply means this isn’t your thing, and that’s fine, we’re all different, but if you’ve made it this far through all 3 long winded articles, then you probably already understand.
I had a great deal of fun building this machine, I learned a lot along the way, and ended up with a neat little retro computer that will provide me with countless hours of entertainment. From here I will be doing a follow-up article to cover more of software side of things, changes that may have been made, and share why I think an old-style homebrew computer like this can actually still be fun and useful. For now though, I’m just going to enjoy the fruits of my labor and say thank you for taking the time to read through all of this. I hope you found something helpful here, or if nothing else, it was entertaining.
Read The Build Follow-Up - What Can It Do?: https://theclassicgeek.blogspot.com/2022/12/z80-mbc2-build-follow-up-what-can-it-do.html
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