Binary Dinosaurs Computer Museum
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Recursion 2016
Sometimes I forget myself how much work is needed in keeping 30-40 year old machines going. A lot of collectors have a policy like 'power up once a year for everything' which might be good to see a boot screen or a READY prompt but doesn't really show the state of an old dear who hasn't been fully exercised since the early 80s. I've been guilty of that myself, particularly after a car boot sale find - plug it in, yay it works (or boo it doesn't, add to 'the list'), catalogue and put it away for another day.
For example, Spectrums used to be easy - WHSmith 'data recorder' with a tape copy of Manic Miner or Jetpac and you were away. These days not so. Both tape oxide and tape recorder belts are breaking down and while it's fairly easy to replace the belt once you know its specs it's not so simple with the tapes themselves. The vast majority of work these days is based on emulators so while there are loads of disk images, tape images and ROMs kicking about they're aimed at emulating on modern hardware since not many folk have the original machines running.
Even with the most excellent World Of Spectrum resource I still had to get something running on actual silicon. There are ways and means of course, playing in a WAV of a game to the real EAR port being the most basic. This is slow however, and in the inevitable event of a crash I didn't want to spend ages reloading a game. Floppies were right out with only a month to go but my Microdrives still worked, or at least 4 did out of 12 :)
Still the problem remains of getting a TAP or TZX file onto a microdrive. Enter Paul Farrow of Fruitcake who's spent a lot of time making boards and components to make Speccy owner's lives easier. One of his mods is a BASIC ROM that intercepts LOAD/SAVE calls and redirects them to the serial port of an Interface1. This one should be a no-brainer but brings another modern problem to the surface - serial ports on PCs. There aren't any.
Obviously there are USB-Serial adapters (mostly based on the Chinese CH340/341 chipset), MAX232 level shifters etc, but none of these worked reliably because of grounding issues on the signals. Fortunately my laptop has a genuine RS232 port which helped, and I ended up building a windows98 PC out of scrap parts just to get a couple of real serial ports AND a parallel port. Also a 5.25" floppy drive. Remember those?
Paul was very helpful, even modifying his Interface1 driver because my testing found a timing problem, and once I'd taught myself how to autostart microdrives (or even use them properly since I never had one back in the day!) that was a platform ticked off.
Richard at the school expressed a preference for Oric-1s so naturally they had to feature. I knew I had a Cumana disk interface and 'big floppy drive' for the Orics as well as a modified Atmos which would be great to show. Machine was easy since it was in a big box marked ORICS, only it didn't work and further testing showed that neither did any of the power supplies. This in itself brought on ANOTHER question. We all know the Spectrum is powered centre-negative which is the opposite way round to the vast majority of other machines of the day. Many people have blown one up just by connecting up the wrong 9V PSU. Is the Oric also centre negative?
Official specs don't say, and much searching showed people saying both ways which obviously didn't help. I didn't have time to scour schematics and eventually the answer came from Dave Curran over at Tynemouth Software when he described the power inputs as odd because it uses the 7809 -5V regulator instead of the more usual 7805. Odd because this regulator is wired to accept +9V and put out +5V so there was my answer - centre positive on the PSU.
With power sorted and an Atmos with a working ULA found I came across the next problem of long term storage - physical keys that stop working over time. Since I was running out of time myself I replaced one keyboard with a spare NOS one I found in an electronic thrift store in Toronto many years ago. Best CDN3.99 I've ever spent :)
Cassettes were giving me a similar problem so I shelved the Orics until I could find the Cumana interface and floppy drive, it was here somewhere. Next up was the Enterprise 128 that's always popular at exhibitions largely because people have never seen one before. It should have been a great British success story but problem after problem hit the team and when it eventually came out in 1985 it was a year late and the company folded not long after. Brilliant specs for its day, the EXDOS interface was even MSDOS compatible so getting games transferred and running shouldn't have been a problem.
Trouble is, my 'exhibition' machine had developed keyboard faults over the years and my other spare 64 couldn't see the EXDOS interface. Much work helped by the folks at Enterprise Forever and the mainstay that is Nemeth "Zozosoft" Zoltan eventually got some life out of my brand new EP128. Then there's getting a working 5.25" floppy drive...
These days we're spoilt into thinking things 'just worked' back then so it was fun discovering that while the floppy drive interface might have been a standard not much else was - single or double sided, single or double density, different track sizes, different drive capabilities set by jumpers and obviously now failing magnetic media with not much documentation around for the more esoteric drives in my collection. Getting a working setup took a couple of days which also included adding a drive to the Win98 PC mentioned above.
Pity that on the day the floppy drive on the EP is the one thing that let me down, but hey.
Memotech MTX512 next and another steep learning curve that resulted in several working MTXs and working FDX floppy subsystem thanks to Memotech fans and my own bloody-mindedness. No games though, see above about cassettes :) Claus Baekkel of MTX World has written an RS232 transfer utility but I couldn't get it working so that's still on the 'todo list'. In the end that one had to be shelved too because after a search that turned my garage upside down I found the box with my Oric Cumana disk stuff in as well as the diagnostic disks for my STM Pied Piper which I'd thought of as long lost.
Much swearing, jumper setting and reading old posts at Defence Force (a still active Oric users forum) resulted in a successful write of an Oric disk image using the WRITEDSK utility. Clincher in this one was setting the drive type to a 360K in the PC's BIOS. Remember that? :) I then played Defence Force the game for a long while because it's basically Defender, one of my favourite games of all time.
I've not had a running SAM Coupe since 2005 and the intervening 11 years haven't been kind to either of my machines. The floppies in my boxed original were full of collapsed rubber since they were belt driven Citizen micro-floppies and my usual exhibition machine wasn't playing nice either. Fortunately just a good clean got this one going, also finding the correct SCART cable to drive a TV. Things I Learned number 128 - not all SCART cables are created equal and some will auto-select the AV channel on a TV, some won't. I didn't know this. Post exhibition I found 'Modernradios' on ebay who still stock replacement belts that are compatible with the SAM floppies.
Once again because of the architecture of the SAM most of the games I had were Spectrum conversions. One game I had at the Crodyon '05 exhibition was the SAM version of Manic Miner and typically the floppy containing it had broken down. At least the SAM has a 3.5" floppy drive so media-wise there isn't a problem transferring from an old PC. An excellent bloke called Simon Owen has written SAMdisk, a utility to convert SAM disk images back to real floppies as long as you have a pre-XP machine capable of fully controlling the floppy drive. A couple of downloads later and I had Manic Miner running again, sweet.
Suffice to say none of the 3" drives on my Amstrad CPCs or later Spectrums worked and I didn't have time to get new belts in. Post exhibition however I've revived all of them as well as fixing worn-out power switches on my CPC664 and CPC6128s. On the 'todo' list is my CPC6128+ which looks like it has bad RAM. It also will have a broken floppy...
Every collector has bunches of ZX81s and I'm no exception. I've spent time upgrading some of them because why not, so I have composite video machines and ones with internal 16K RAM etc. One thing I discovered after hours of trying is that NONE of mine will load a game and it's a problem I still haven't solved. The only real way of loading with a ZX81 is still via the EAR port and you'd think that feeding it a pure WAV signal from a digital audio source would work 100% of the time.
Not so, and reading the forums it's a problem for everyone. With the lads at Sinclair ZX World I tried all sorts alongside half a dozen different loading utilities in all operating systems I had to hand. Nothing worked apart from one of my composite modded machines which promptly showed screen tearing on QS Defenda so I gave up on it. Post exhibition I discovered that game does the same thing on an standard RF telly....grr...
Speaking of TVs, another casualty of the 2005 Croydon exhibition was one of my 70s B&W portables which quietly let the magic smoke out of its mains filter capacitor so I turned it off and didn't touch it until June this year. It took an afternoon just to replace one RIFA capacitor and thankfully the TV worked fine afterwards and ran the Grandstand Pong at Recursion. Yay old TV technology :)
In the end it took me 6 weeks of constant night-time/weekend working and an entire week off actual work to get enough machines going for the show and it was worth every minute. I've learned a lot more and hopefully this document will jog my memory next time I have a problem and commence light swearing.
For my own reference if nothing else here's a list of the forums that helped:

World Of Spectrum
Tynemouth Software
Enterprise Forever
MTX World
Dave Stevenson's MTX pages
Defence Force
Sinclair ZX World

Thanks folks!

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