Watch on YouTube: https://www.youtube.com/watch?v=11sqTJXXSQo
Exploring The Cefucom-21 Japanese English Language Teaching Computer
Introduction
This is the Cefucom-21, an English language teaching computer from Japan - and it’s very weird. So let’s see what it’s all about!
Script
I think it’s fair to say that I have something quite interesting to show to you today. You see, I won this machine on one of the Japanese auction sites a couple of weeks ago, and in the few weeks that I’ve owned it, it’s only raised a lot more questions than answers. For example, this thing on the side, which I assumed from the photos was some kind of screen - like a CRT or an LCD - turns out it actually isn’t, although it is a display of sorts, and of course a bit later on in the video we will have a look at how that works.
But for now I wanted to put this out there not only as an initial exploration of the hardware and sharing the few bits of information that I have managed to track down, but also as a call for help really, for anyone else out there who might know a bit more about these machines than I do. I have tracked down one person in the UK who owns one of these - in fact he actually owns two of them - and he has been incredibly helpful in sharing photos of some of the extra bits and bobs and the information that he’s managed to put together, but it turns out that neither of his machines actually work either, so he was very keen to see whether this one worked - and we’ll also talk about that a bit later on in this video.
But for now, Let’s have a look around it and try and work out what it’s all about.
So, what exactly is this thing? Well, it’s a Cefucom or Cefucom-21, and on the front it says “CCI Multipurpose SLAP Computer”. Now, I’m not quite sure what SLAP actually stands for, but I do know that it is something to do with language learning, because this was actually sold in Japan as an English language learning solution.
Hardware-wise, it’s based on and reportedly 100 percent compatible with the Sanyo PHC-25, and if you’re familiar with that machine you will no doubt have noticed that the keyboard looks very, very similar indeed.
According to 1000bit.it, which I will link down in the description along with any other information I have, the specs of this thing are quite, quite interesting - so it was released in 1983 and supposedly has 52 kilobytes of RAM, with 6 kilobytes of VRAM. It has a Z80 CPU running at 2 megahertz - or is that two Z80 CPUs running at an unknown number of megahertz, I’m not quite sure, hopefully we can find out in this video - and it runs Cefucom Basic 1.0 and reportedly has one graphics mode, which is 256x192 at nine colors.
Finally, it has a built in tape deck that supposedly supports a data rate of 1200bps, it has a Centronics parallel port - and mine actually has a few extra ports on the back as well, including joysticks, which is quite interesting - and it supports RF and composite video output.
You’ve no doubt also noticed the port labelled “Coupler” in this area, and there’s actually a power pass through for this, where the main power cable comes into the unit, along with pass throughs for a printer and a TV. Now this actually came with its original manual - in fact, believe it or not, it was in the original box, with the original polystyrene and the original plastic bag and all the accessories as well - so I don’t even know if this has ever actually been used. But on the cover of said manual, there is a picture of this machine next to a matching acoustic coupler and printer - so it would make sense that they were available as accessories. The coupler, of course, being a type of modem where you would place a phone on the top and it would allow it to connect to other machines or perhaps some kind of network service.
On the side is a port labelled “ROM Cartridge”, which I can only assume allows it to load those Sanyo compatible cartridges, but it seems that the software for this was mainly distributed on cassette tape.
So, I mentioned earlier that I’d been in touch with another UK-based Cefucom-21 owner, and he goes by the name of “HereBeDragons” on social media - he’s one that you may have come across, he’s also heavily involved with the Centre for Computing History in Cambridge, where he organises some quite cool events and things. Also, a massive fan of the Dragon32, that amazing computer from Wales, which I have covered previously on this channel - and he has provided some very useful information and some photos that go along with this - so he managed to track down the original software packs for this which were shipped on cassette - and there are some interesting looking photos here - so they came in these blue binders and they had titles like “Using Personal Computers” and “Daily Life” and that kind of thing.
But I think the really interesting and unique thing about this machine, which we’ve managed to piece together, is to do with this rather chunky looking cartridge - and indeed, there’s also a picture of this in the manual that kind of shows how it works - so as you can see, it has like a cartoon image on the front, and a couple of what I would describe as gears or sprockets on the end - and the internal mechanism built into the Cefucom-21 looks like something out of a printer or something and evidently kind of drives this thing directly, so what we think happens is that as you progress through the English language lessons, there’s an accompanying picture that comes up on the screen and it’s basically an endless loop of paper that has all of these images printed on it and the computer just winds its way through them as the lessons progress - and this is in addition to the image that would be displayed on the TV screen as well, of course - so, a really, really interesting and unique setup.
Again, big thanks to Tony for those additional images and also the additional information. It’s been absolutely invaluable in trying to work out just what the Cephucom 21 was all about.
Unfortunately, along with those images, he also sent a warning - and as you can see, this is to do with the internal battery. Now, sadly, this is all too often the case with these older machines - the battery leaks over time and can do quite a lot of damage to the PCB, and that has indeed happened to his machine so I absolutely, as a top priority, need to get the battery out of this machine. But to be honest, that gives us an opportunity to have a poke around inside and see how all of that works as well - so let’s do that now!
And this thing is quite large, as you can probably see, and it has a lot of screws in the bottom - in fact, the only screws I can see on it are on the bottom here - so I’m guessing this whole bottom part comes off.
I’ll just remove the cartridge slot. So we have the audio connectors here, and of course there are wires that go to those, but that looks like that board should just unclip, I think.
Yep, that’s easy enough - and there is a ribbon cable going to the cartridge port.
How does that work?
Ah! Easy peasy, so that just unclips as well. Very nice design, actually - quite serviceable.
Ah, okay, so as I was unscrewing the screws, I did hear something drop down inside on a few of them, and it would have been these plastic blocks. It looks like that these were once glued onto the sides there, and evidently the glue’s given up over time so they should be easy enough to glue back on - and it looks like we have a few of those.
The front screws went straight into there and thankfully they are all the same length, apart from the screws that went into the motherboard here - and there was one kind of here- it must have been this one- kind of here-ish as well. Maybe as we take these boards out we can rescue those plastic blocks. So what else do we have here? We have a big transformer, which of course is connected to the mains input - so that all makes sense. We have a fuse here, that’s the cassette mechanism that we saw on top, and this is that screen mechanism - and it looks like, ah, it looks like there was something belt driven here, and that looks like the remains of a belt, which is not good!
But that’s, to be fair, that’s probably come from the the tape mechanism.
Interesting - and there’s like an elastic band here - this is for driving this screen thing, this paper cartridge mechanism here - and that looks okay. That’s actually intact so I won’t touch that.
I would like to know where that belt came from…
But of course, our job for today is to track down that battery - I’m not quite sure which of these boards it’s on - you probably can’t see from this camera angle, but there are actually one, two, three, four stacked boards here with risers between them - so I’ll get all of those out and we’ll see where we are.
Ah, this is very good news indeed - so this is the battery and we have some leakage just starting on one end, but it hasn’t actually spread as far as the rest of the board - and the other end is perfectly fine so that is looking great - so I’ll get that out in a second, I’ll get the soldering iron out and desolder that, but first let’s just have a look at the rest of this board and see what we can see.
Okay, so I’m back, I’ve been Googling datasheets frantically, and I think I’ve worked out what’s going on with this board here - so, this is indeed the brains behind the actual operation, this is our Sanyo PHC-25 clone, and the board is completely different to the board in the Sanyo, so it’s not like they bought a job lot of Sanyo PHC-25 motherboards and just stuffed them into these machines, this is very much a custom designed thing. We have that Z80 CPU just here, and from what I can see, there’s only one of those, at least on this board - there might be additional CPUs on these other boards for controlling other things, I’m not quite sure - and we have this chip here as well, which is the PIO chip for the Z80, so that interfaces it with various other things on here.
Supporting those we have these LH0082As, and these are Z80 CTCs - so these are timing chips, there are two of these, and they just handle the timing of everything on this board to keep everything in sync.
Over here we have two SRAM chips - so these are asynchronous static RAM chips and they are 16K each - so of course 32K in total. We have three of these programmable peripheral interface chips here, which I’m guessing wouldn’t have been present in the Sanyo - and of course, these are to interface this with all of this - I mean, there’s a fair bit of hardware here that we need to control and that we need to accept inputs and outputs from, so it makes sense that there would be a whole load of IO on this board.
We also have some EPROMs here, which I’m guessing contain the operating system, and finally, the only other thing of interest on this board - obviously we’ve got some 7400 logic just tying everything else together - but the only other thing of interest is we have some of these 4116 video RAM chips - so yeah, as per that spec that we found earlier on the internet, the video RAM is separate to the main system RAM and we have eight of those in total by the looks of it.
And of course while we’re in here, we’ll also remove our troublesome VARTA.
Yeah, just some ever so slight leakage there just into the ground plane, but certainly nowhere near as bad as it could have been - and I think we’ve managed to get to this one just in time!
Oh my goodness, this is not what I was expecting to see at all - this is really weird - so I’m going to take back everything I said about that previous board being the brains behind the operation, because, well, there’s even more brains on this board, evidently it’s split across multiple PCBs. We have that second CPU, which that spec that we found seemed to imply this machine would have - so indeed it does have two Z80 CPUs, and of course we’ve got the PIO chip that goes along with that. We’ve got even more RAM, so we have two more banks of those 4116 RAM chips, and we’ve got three of these 16k RAM chips here as well.
We have four more EPROMs and I’m not quite sure what they might contain - I guessed that the previous set were the operating system, but who knows? I’m probably going to have to get all of these out and dump them - and if I am successful, of course, I will link that down below so you can check it out - not sure if it will be of any use to anyone, but seems worth preserving while I’m in here.
This, of course, is the video output section: we’ve got our RF modulator circuit there, which of course goes to the RF output, we’ve got composite video output as well - and this chip is really interesting to me - so this is the MC6847P, and this is the video display chip that was used in the Dragon32, and the Tandy CoCo, the Tandy Color Computer - and there we go, apparently it was used in the Cefucom-21 as well!
And finally, speaking of chips that are of particular interest to me, of course there is this sound chip here, the AY-3-8910, which is an iconic sound chip in its own right - it was used in lots of different arcade games and machines back in the day, but perhaps of most interest to me, of course, it was the basis for the YM2149 sound chip that was used in the Atari ST - so a really, really interesting board here!
…and finally, just in the name of completeness and in the name of getting this thing documented, this is my third and final board to look at today. I know I mentioned at the beginning that there were four in here, but it seems the fourth one just has a couple of connectors on it - it’s just where some of these wires go and kind of interface so I have enough of a rats’ nest of wires and screws and standoffs and stuff to deal with as it is - so I’m going to leave that one in there for now. But this looks like it’s power related, I think - so we have capacitors on here, we’ve got some big resistors, we’ve got loads of transistors, we’ve got what look like motor drivers which I guess are for driving the the big motor on here for that paper cartridge interface thing, and of course, we’ve got the cassette deck as well so that’s our power supply board - and now I’m going to see if I can put all of this back together and hopefully when you next see me, I’ll be in a position to get this thing fired up and see if it actually works…
So we find ourselves in a position where we have a loosely reassembled Cefucom-21 all ready for testing - so I guess it’s about time we actually tested it.
Yeah, unfortunately it was not to be, so apologies for that - that’s just how it goes in this hobby sometimes. I’ve checked all the obvious things: I’ve tested the fuse, I do have the manuals - I’ve scanned the manuals for this and also Google Translated them and I will make those available down in the description - so I went through the manuals just to see if there was anything obvious that I was missing. It does have a weird built in alarm clock mode, apparently, which I was going to demo, and I thought maybe if it was in the wrong mode, or the time wasn’t set, or something, that maybe that would prevent it from powering on but no, apparently not, apparently I am doing it all right, and it’s just dead - so, evidently, it needs some more diagnostics. But Hopefully this video will serve its purpose anyway of just getting the word out there - of course, if you know anything about these machines or you can track down the software or the cartridge things for me, I would be very, very interested in that so please do let me know - and of course, on that note, a big thank you to Tony for providing those additional images and the additional information. It was really, really useful to me so thank you. Please do go and give him a follow over on Short Circuit and HereBeDragons on the social media sites as always.
But that’s all I have for you for this video so if you want to see this thing working, hopefully at some point in the future, please do subscribe to the channel so you don’t miss out on that. A big thank you as always to my supporters on Patreon, Ko-Fi, and the YouTube channel membership page - and all that’s left for this video is to say thank you ever so much for watching, and hopefully I’ll see you next time.
Original Video Links
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Relevant Links:
ROM Dumps / Manual Scans: https://ctrl-alt-rees.com/hino-electronics-cefucom-21-information-and-downloads-manual-scans-eprom-dumps-and-more.html
Specs: https://www.1000bit.it/scheda.asp?id=1767
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Centre For Computing History Cambridge: https://www.computinghistory.org.uk
Additional Thanks to Re:Enthused: https://www.youtube.com/ReEnthused
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