While the last few weeks have been busy, they haven’t been that busy on a retro front.
I realised I’d ordered the wrong Floppy Disk controllers for the Microbee and the MSX controller, so I had to order replacements. They’ll take quite some time to get here, but that’s OK. Due to some financial commitments in my life, I can’t quite afford the many parts to finish either project at this point. This pinch will go away soon and I’ll be able to get a bit more aggressive with my parts purchasing.
As it is I have been able to get quite a lot of parts, only to run out of solder, of all things. Oh well. Next fortnight I guess.
Despite the tight budget, I did get two more systems, thanks to a reader of this blog (Hi Richard!) who has given me his old computer system collection. There’s some really interesting stuff in here.
First up we have a classic “breadbin” Commodore 64. The power supplies on these models have a fatal flaw where the 5V rail will creep up and up and eventually burn out the system, so for now I have put it aside and used my own dedicated power supply.
On power up it presented a familiar blue screen of happiness. Further investigation, it looks like the SID sound has failed. I have confirmed this by trying the chip in a working system. Down the track I will purchase an ARMSID replacement. It will be nice to have both styles of C64, as my other units are all the later C64c styling. It’s in really nice nick.
When Richard lulled this one out, I was astounded as I was expecting a “classic” BBC Micro Model B, possibly with one or two external drives. This is a much newer and stranger creature. This is a BBC Master Compact. It has more RAM, and the power supply and disk drive have been combined into what’s referred to as the “Monitor Stand”. (It’s the bit underneath the main unit there)
I inspected the power supply and discovered a very mazed X2 RIFA capacitor, so rather than try and power it on, I dug out a suitable power supply from my stash and plugged it in to the main unit.
On power up it emitted the long familiar “Booooo Beep!” of the RAM test being completed and the system booting. (If you have ever used a BBC Micro of any type, you’ll know the sound)
Some of the keys weren’t working so I couldn’t test it very far but I was able to write the usual “Hello world” program, albeit without being able to use the SHIFT keys or the space bar. More on that later.
I was able to get to my local electronics store on Thursday evening and purchase a replacement X2 cap. This one is not Mica filled so should have a longer life.
Some quick work with the desoldering gun and out the old cap came and in the new one went, using some of the “scrap” solder I have on hand. (It just needs a bit more flux). I also cleaned up the power supply while I was at it.
I need to mention the faintly bizarre way to get into the monitor stand at this point. As it has mains potential and has some juicy capacitors, it’s all marked as being “no user serviceable parts”. If you need to get in, here’s how to do it:
Firstly the front plastic bezel and the back plastic bezel simply pull off away from the unit. The side plastic bezels rae a lot trickier as they need to pivot on hidden lugs. They pivot on the base so pull from the top. (I was really terrified I was going to crack something in these old brittle plastics but it was fine in the end).
Next there are 4 metal screws on the underside. Once they are gone, the top cover is now free to simply slide off the main unit.
A little bit of research revealed that the keyboard on the Master Compact isn’t a mechanical keyboard like older units, but is a rubber dome system. I opened it up by removing about a million screws, and cleaned all the contacts with isopropyl. For the space bar and the SHIFT keys, I also cleaned the carbon contact on the rubber domes gently with an ink eraser followed by a dab of isopropyl on a cotton bud.
Now everything had either been repaired or cleaned, I gave the system a go and it works perfectly now. I have no plans to upgrade this one at this juncture, although I am eyeing up some internal upgrades to make booting games easier.
The rest of the haul
Richard also provided two CRT Monitors, a printer, some BBC Compact software, a datasette for the C64 and a bunch of cables, dust covers and even a tray hand made to hold the C64.
Looking at the monitors, there’s a 14″ Thompson branded monitor (Model CM 36632 VPR, which I can find absolutely nothing about on Google) with a SCART in. It seems to work OK, for a screen of this vintage. The power button is a bit gummy, so probably needs opening and cleaning.
Next up is a 12″ Taxan (Model KS12R305S-AN, also a mystery on the internet) with a pair of mystery connectors. The cable I have doesn’t seem to match either the C64 or the BBC so I’m at a loss as to what it should plug into.
There was also an Epson LX-800 printer, complete with tractor feed. It’s a parallel port printer, so compatible with several of my systems.
I completed the ROM switcher for the Microbee. It mostly works, insomuch as I can choose a ROM easily enough. Only thing is, the second ROM in each pair is always the same. Not sure what is going on there. I’ll need to research how the bank switching is working.
I spun yet another spin of the Microbee case. This one is extremely close to being “right”, to the point that the ‘bee is currently living inside the prototype. There’s some minor tweaking on some holes to be done (There always is), and one of the braces was out by 3mm because I measured its location from the wrong reference point.