The label on the top of the tube reads "Danger - Hazardous Voltage Area 12kV". CLICK HERE to download the circuit diagram. With the exception, that is, of the transformer which I somehow never got around to bolting on and which consequently dangled perilously from a few wires. These items can be seen bolted to the right hand side of the monitor chassis. The big capacitor mostly solved that one though. The vertical refresh rate generated by the graphics circuit was 50 Hz derived from a 16 MHz crystal oscillator, and did not match exactly the 50 Hz UK mains frequency, hence the interference. Such a large capacitor turned out to be necessary in order to prevent the picture getting wobbles which moved slowly down the screen. Nor does it have a power supply, so I had to build a simple one consisting of 16 volt transformer, rectifier, 1-amp 15-volt voltage regulator, and a huge capacitor. As you can see from the photograph, it hasn't got a case. O Keyboard: 1980s Maplin experimenters keyboardĩ-inch Black & White monitor by Phillips The monitor I purchased for £15 from Bull Electrical near Brighton. O Graphics display: 512 x 256 pixels, 256 grey scales O Memory: 32 KBytes RAM + 128 KBytes Display RAM Tragically the boards are lost so I have no photographs, but I have all the circuit diagrams and will explain a bit about how it all worked, and tell the story of this long and hard struggle!įirst, something about the specifications! I hadn't even finished the sidereal clock before I started the Z80 project though. Shortly after I started work on my Sidereal Clock project, which was probably a less ambitious way of learning some digital electronics (although still a hefty project!). I reckoned if I gave it the HALT instruction I could get the LED to light, and indeed it did, but that's about as far as it went. I did build some stuff and had an LED connected to the HALT light and a 8-way DIL switch on the bus. I probably bit off more than I could chew at this point. What tends to happen is that I read an article, understand something of how their circuit works, in this case how to build a Z80 computer, then my imagination gets carried away with how I might design my own. Like many of my projects, an article in an electronics magasine inspired the project. The Great Z80 Computer project was originally started way back when I was 13 or so, must have been about 1984 or thereabouts.
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