Tag Archives: Electron

More Lego “8-Brick” computers!

I had a lot of interest in the Lego ZX81, you may be interested to know that I’ve also been working on others as well in Lego’s Digital Designer software. Some are closer to completion than others. Here’s what I currently have on file. Will they make it to real Lego models? Hopefully, yes. Sadly Lego closed down the service that gave me a proper kit in January, so I’d have to order future models brick by brick. No exciting box or instructions!

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Sinclair’s follow up to the ZX81 – the ZX Spectrum. This is almost done – I’m in the process of seeing if I can reduce the brick count on this model a bit. The red 1×4 plates sticking out of the base of the model is there to help the software “lock” the lid on (so I’ll know if it all fits together). Eventually, there will be flat plates there, which will allow the lid of the machine to rest on the top without being fixed. Much like the ZX81 model, the Spectrum has a PCB inside. I may include a Lego Rock Dickinson minifig with this one if I can find a picture of him from the time!

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Cambridge Computers Z88. This was Sinclair’s computer post Amstrad sale (Sinclair sold the name as well as properties to Amstrad). This is a little less developed as a model. I’ve got the screen, keyboard and base plotted out. I have to fix the screen to the base, put in some PCB stuff and check they all fit together. And, yes – those are batteries! The Z88 ran on 4 AAs.

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Acorn Electron. This is moving on, but I have a small problem with the keyboard. Unlike the Sinclair machines, which had their own more unique keyboards (which lend themselves more to being modelled in Lego), the Electron had a full size keyboard. The problem I am having at the moment is that there is no Lego brick that looks like a key. So what I have done is made an impression of them out of existing parts. I am not sure if these will make the grade or not. If you have any thoughts on the keys – do they work for you or not? – then let me know in the comments below. Remember, this is Lego, which is a fairly low resolution thing (something I like because 8 bit computers had pretty low resolution graphics). I am looking for an approximation – something which will work within the confines of the medium.

If I can get the keys right for this model, then this opens the door for other machines with more traditional keyboards – most notably the BBC Model B which will be a major undertaking, and will (for me anyway) be the flagship model. I plan on that one being a representation of my own BBC Micro, complete with internal expansions on the motherboard. It’s a big thing, and costly, and I want to get it right. Minifigs of Chris Curry and Hermann “Your Prussian Friend” Hauser may well join the BBC Micro model.

There is an Atari console in the loft. That will get the treatment eventually too. It has those iconic joysticks, which should be fun to model.

Firing up the Electron

I have an Acorn Electron. It’s the second one I’ve owned. The first being a rather temperamental example that I bought in 1984. It kept breaking down, so I managed to get my money back on it. It was spending more time being mended that I was using it for playing Elite hard work and study. To be fair, it did kick off a project for my computer studies at school, but that ended up being completed on a more powerful BBC Model B there.

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This Electron came my way during the last few weeks at University. A lecturer had one in his office, and I just happened to tell him what it was. I was actually quite surprised to see one, especially in this configuration. He said I could keep it. He didn’t want it, and he didn’t know what he could use it for anyway. So, I took it home, and borrowed a power unit which would work with it to test it. It worked.

What this is is an Acorn Electron (the bit with the keyboard), and two extra add ons which bolt onto the back. The Plus 3 is the 3.5″ disk drive, and the Plus 1 which has cartridge slots, as well as a joystick and printer port around the back. The Plus 1 was fairly common, but the PLus 3 was less so. I don’t think I ever saw one outside of the Acorn User shows I used to go to.

It’s been bouncing around the place unused for a long time. The problem with not being able to switch it on was the lack of a power adapter. It’s a bit of an odd specification – 21V AC – nothing I have offers that kind of juice, so I turned to eBay. It was a while, but eventually something turned up. An unknown “Acorn” branded power supply – 21V. The seller didn’t know what it was for, but in the photo was the plug – with the letters “ADFS” in Dymo lettering. To someone who knows Acorn hardware, this means “Advanced Disk FIling System” – and that is just what the Electron Plus 3 has. This was, I surmised, the long lost power supply unit I need to run this machine. I bought it, and it arrived last week.

The Electron started up – but there was a problem. Right near the plug that connects to the machine was a nasty kink in the cable. This was causing power fluctuations, as well as, at times, failing power ups (and odd display artefacts). A trip to a well known electrical store and an adventure with a soldering iron later, I was able to test the machine with a healthier looking power lead.

It wouldn’t start! Yikes! Had I broken it? My thoughts were that there may be a bad connection somewhere between the expansion units, so I unbolted the PLus 3 and Plus 1 units, gave the connectors a wipe, and reassembled the machine. I knew I could not just test the Electron on its own – the voltage would probably cause it to really pop a fuse, or worse. So it had to work with the Plus 3 connected.

Power applied again, and…

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It started. The picture on the modern TV is excellent, and it remained up and running without any further power fluctuation oddities. I was surprised that the modern TV coped so well – bit it has some nice backwardly compatible sockets, and upscaling the picture to that size didn’t seem to be a problem.

Next step – sourcing a Welcome Disk. That has the all necessary formatting and other disk management software which wasn’t put on the ADFS ROM. It seems that Twitter may be answering that particular problem.

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More on this project as things develop.

See more photos of this machine here:

More about Acorn Electrons here:

The Acorn Electron

I had one of these once. The Acorn Electron was the little brother of the BBC Micro.

See more here:

It was a nice little machine, despite its weaknesses – slower processor, only one sound channel and no Mode 7 (Teletext) graphics. It was a great little machine, but it did suffer from production problems – a lot seemed to go wonky. I got through a few before I gave up and got my money back. I was able to get a BBC Micro with the refund a bit of extra saving.

This particular model came my way several years later, and it has the two official Acorn expansion boxes bolted on. The large L shaped one is a Plus 3 – a 3.5″ floppy disk drive, which gave the Electron Acorn’s ADFS, as well as much faster loading times. This, dear reader, is the time when most software was loaded off tape, and it took ages.

The box at the back is the Plus 1. This gave toy the joystick port (actually, it did more than joysticks, being an analogue input port), and a printer interface. At the top are two cartridge slots. You could buy games and other software which loaded from them. The aim was to store the software in a form which could be run straight from the cartridge, but it seemed to be the practice to treat it as another filing system and load games into the main memory. There were other add ons which plugged into these slots, including a floppy drive from a third party, and if memory serves me correctly, a teletext system.

You can see from the photos that the Plus 1 & Plus 3 connected via edge connectors to the Electron, and are held in place by some pretty hefty screws.

There was never a Plus 2. I wonder what it would have been.