leaded solder

This is super cool. Good luck with making the portable version!

How did this turn out? I have an FZ-1 that seems to work fine except when interacting with a disc drive/ODE (3DO logo, then black screen, no attempt to spin up the disc) and I think the problem is bad solder joints on the CLIO IC as a result, but I haven't had a chance to get the board out to fix it.

If you had an intact enough boot you could probably make a mould and do your own silicone boots, but that sounds like a big project. Maybe you could make a leather boot like for manual transmission shifters? Lots of places make those and it would be kinda classy, although the 80s vibe would be lost. What's the value on the pot? You might be able to do some trickery to rescale a more available one.

I've had similar concerns about the ease of assembly on my board, as I have trouble getting a reliable assembly even by myself: considering doing a port to through-hole components and a much larger board. Might do an Adam instead to absorb that change, that's a solid idea. Through-hole assembly is even more expensive than two-sided surface mount... As for development/hobbyist tools, I have about half of a CamelForth port for the Sega SG-1000 on the go. I got stalled trying to write a keymap decoder because I wanted to do it a fancy, efficient, cool way instead of just actually doing it 🤪

A $20 logic probe like the LP560 on Amazon is probably a good starter if you don't want to buy an entire scope just to check for a clock signal, but it's likely you'll want to move on quickly after that to find things like malformed/weak signals etc. It's really annoying to use one to figure out a compound problem like "jumped to a crazy memory address all of a sudden." RAM sounds like it's a 16K x 1 4516, which based on a quick check is not super easy to get. You could maybe make a double-socket adapter or lift out a pin for a 4164 to work, as the pinouts seem to be close but not exact (have to tie up the a7 line and "waste" part of the 64K.) That page also lists the MB8118 as compatible, which seems to be easier to get from AliExpress, but just barely. Edit: Apparently I screwed up my research. It's not hard at all to find mk4516 on eBay.

The "standard" pin spacing on a board that uses DIP parts is 0.1" (or 2.54mm.) Armed with that knowledge you can sort of guess that the 0.3" number is for row spacing, but I agree it isn't clear at all in the Digi-Key listing. For 80s stuff, ROMs, static RAMs, video chips and CPUs tend to have a double-wide 0.6" row and 74s are almost always 0.3" wide. I don't think I've ever seen a double-wide (0.6"/15.24mm) 20-pin DIP IC, but I'm sure they exist: Digi-Key sells some sockets for those too, although they're very expensive and out of stock. You can also get cheap dual wipe sockets of all kinds of common sizes (including 20p) in a kit from Amazon, although Digi-Key has a much higher quality floor for their parts than Amazon. I use a kit like this (the one I actually bought is no longer in stock) primarily as an organizer for loose sockets and buy more from Digi-Key as I drain them building boards.

It is sort of surprising that they went back and rewrote Donkey Kong, and now I wonder what versions I have. I guess being able to shove it onto a smaller ROM IC must have paid for that work and then some.

I found this listing of Japanese GBASIC keywords, in case this helps anyone tinkering with it. I used it on my own blog post when I was setting up my new-to-me Pyuuta mk1, although the keyboard is still really finicky and I have to fix it. My post has a translation of a very limited handful of keywords, though I intend to go back and do all of them later.

Yamaha had contracts with a lot of people outside of "just" home computers and musical instruments, I suspect. Japan also has/had a law essentially requiring pachinko machines to be scrapped or exported a couple years after their date of manufacture, so there's a lot of those made every year, then later going into scrapper inventory along with their audio chips. Nowadays I bet they're PC-adjacent hardware or at least something that uses cheap sample-based audio, so the supply from pachinko and pachislot is gonna dry up. I have heard other people in the past speculate that the AY-3-8910s are mostly blacktopped YM2149s – from memory, they're mostly the same but the Yamaha clock is doubled.

I just got ahold of an NEC PC-9881K2 dual 8” floppy unit. It was super cheap on Japanese auctions and I felt bad for it, but I probably should have paid more attention to how heavy it is. No idea if the drives need mains power but that make things more complicated if they do, as the power supply has been designed for 100V. I don’t have any disks for it, but my goal was to use it to dump any 8” disks I came across with the Greaseweazle. I might try to find some blank ones and figure out how to hook it up to the PC-98’s external floppy interface.

Yeah, there’s a CPUCLK pin that comes off the 9918/9118. Sega used it in the SG-1000, but it wasn’t available to Coleco on the 9928/9929. Not sure what Sega did in PAL countries. There is also a GROMCLK for interacting with TI99 GROMs but I couldn’t come up with a good use for that.

As far as I know, there's only two other ones that have been assembled, other than the ones I've built. I think there's... four or five loose boards out there other than mine? Happy to help if you have questions!

That's a good build, congrats! Using the 9118 to shave most of the video DRAMs is a good improvement too.

The board outline that I used for my prototyping board came from alank2 on the VCF forums. He built a neat modular cartridge that included a RAM expansion - he might still have a couple of those left.

I've got a couple blog entries which all have some attached photos: PC-6601SR/Mr.PC cleaning, floppy drive recap, and weird disk image hacking PC-6001 volume pot repair PC-6001 keyboard cleaning and repair PC-6001mkII pickup (this one is still awaiting me building a replacement keyboard PCB, but I might try ultrasonic cleaning it first) PC-6001 white screen repair (shorted tantalum bypass capacitors at the power entry connector) It is funny, at one point P6s were very cheap/relatively unknown, and now they are starting to go up in asking price like all the other 80s machines on Yahoo! Auctions Japan. I'm not sure what's going on, as I definitely don't see more "activity" about them on the internet. There's a couple things I've been working on, very slowly because other things keep getting in the way: Using a Raspberry Pi Pico to convert the 15kHz 15-colour RGB+Intensity output from the PC-6001mkII and onwards models to 31kHz VGA (maybe about 40% done; Japanese hobbyists have used a sea of 74 logic or a FPGA to do this but I think the Pico is fast enough) The same as before but using a modified cable for the RGBtoHDMI board (this works; I need to configure the palette and finish the writeup) Keyboard adapter/clone keyboard for the PC-6601SR (the computer accepts both wired and wireless infrared keyboards; my keyboard adapter is pretty sketchy but it does work) A serial-port board that fits into the internal expansion slot (I think I've got this one figured out electrically, but not physically, and will have to prototype a few different board layouts until I get the dimensions right) A Gotek mount and "boot drive switcher" board for the PC-6601SR, so I can toggle between booting off real disks or disk images Dumping the 8049 on the original PC-6001 motherboard to try and revive another hobbyist's sickly PC-6001A, as well as improve compatibility on MAME Repairing a damaged PC-TV151 monitor, which is the companion CRT to the PC-6601SR; it has 8- and 15-colour digital modes, JP21 analogue RGB, composite input, Japanese RF, and allows the SR to remote control it for channel switching, computer graphics superimpose, and other features. I've repaired a broken power switch on this one, which has revived something in the low voltage side, and I haven't had a chance to figure out why the high voltage won't switch on. CRTs are still a little scary to me. A whole second PC-6601SR that I managed to win shortly after Christmas, which has a bunch of special cables (for instance, the PC-TV151 computer cable) that need reverse engineering Some PC-6601 floppy games don't work properly on my PC-6601SR, and I think they are probably bad dumps, but I can't figure out why. A lot of these projects get some sporadic progress and then get roadblocked or put aside for months at a time, so don't expect anything quick Some other recent discoveries that I'm aware of in the P6 scene: Another hobbyist has located an Al-Warka PC-6001 (the Iraqi government issued licensed clone of the NEC PC-6001mkII) and is preparing to dump the Arabic BASIC cartridge and English(!) BIOS ROMs Lots of interest in NTSC artifact colour in the Japanese community (the 6847 on the original models has CoCo-style artifact colour tricks, which is not supported in the 8- and 15-colour digital RGB modes for obvious reasons.) Various fun game ports, like this very nice version of Tetris. I don't have any articles up about my prototyping board yet, but I've attached the pinout and a picture of the board.

I have a couple Japanese PC-6001s (PC-6001, PC-6001mkII, PC-6601SR/Mr.PC) but no 6001A/TREK yet. RAM expansion is fairly easy to build: I wired mine on a protoboard cartridge I made, but I've been tempted to design a ready-to-go RAM/ROM cart as it's also very straightforward with the dedicated select lines. For an emulator, I've been using PC6001VX on my Mac.

Anecdotally, my TMS9918As were sourced from AliExpress (utsource would also be an interesting place to check out.) eBay is crazy expensive for components. 9118 is the one that uses 2 DRAMs, 9918 is the earlier part and uses the full set of... eight? I use a 62256 with Leonardo Miliani's design to adapt the TMS9918 to the slower, larger SRAM. I think it would be cool (if extraordinarily difficult) to have a shared-memory design one day. 9118s are a little less easy to get, I had to pick up a few to fix a Casio MSX1 and I found that it was more expensive than a 9918; maybe they made many fewer.

I will have to scope an original ColecoVision to figure out if the clocks are in phase. If they are, a future revision should just use the 3.57MHz output from the TMS9918 directly, like the Sega SG-1000 does (the ColecoVision's original TMS9928 does not have this because they use that pin for one of the YCbCr outputs.) Thank you for the info about that clock generator, it looks like a very useful (and extremely period-correct) part that I'll have to look into further.

This is a super cool project! Great work doing the "last 99%" and getting it to run, CPLD stuff is still a terrifying mystery to me.

I also based mine off the @ChildOfCv schematics. Probably would have been impossible without them, I am hugely grateful. Those schematics were very accurate in my experience, I don't remember and/or haven't noted any errors at all on the schematic side. My bring-up problems were using the wrong footprint, various other rookie mistakes, multiple bad controllers, and trying to get away with a weird Sanyo video PSRAM that I didn't know how to drive. After that, it was all bad solder joints. I did get rid of the original Coleco clock circuit, as I didn't understand it, and just ended up using two clocks, one 10.738... crystal for the VDP and an oscillator for the Z80/SN76489 although I think this might cause the two to be out of phase for some things. It's possible I've made an error there as sometimes it doesn't sound quite right (the background engine noise in Time Pilot seems to be absent, for example, and I remember it being super loud as a kid.) Eventually I think I will use the clock output from the 9918 to drive the Z80 in order to save the buck or two on the oscillator.

Are you going to retain the quadrature controller (Super Action Controller, steering wheel, etc) decode logic? That took up a ton of room on my board – I maybe could have been at 100x100mm without it.

This is a great looking game, I’ve thoroughly enjoyed watching you working on it and trying to cram everything into the ROM space. I’d love to try it on real hardware.

Pin 7 is wired on both controllers to their respective LS541s in the ChildOfCv schematics.

My Gemini looked best with a cable-TV coax cable (very thick, hard to bend) and the RCA-to-F-type adapter linked above. If you do open it up, look for broken solder joints on the controller connectors - both of mine were bad, as was a crack developing on the joints for the DC jack.

My used one came with a cover that appears 3D-printed, but I have no idea if the files are available openly or if anyone else is selling them. I checked on Thingiverse but had no luck.