★ HARDWARE ★ MONTAGES ★ ABBA-THE DRIVE-IN MOVER (AMSTRAD ACTION) ★ |
| ABBA-the drive-in mover (Amstrad Action) | Hardware Montages |
If a drive switcher seems such a good idea, why don't you make your own? PHIL CRAVEN, who unlike ABBA has never won the Eurovision Song Contest, shows how. Not so long ago I came across an unfortunate 6128 user who had a Multiface II and a 3.5" disk drive with 800k storage capacity. His idea was to store lots of games, captured by the Multiface II, on each 3.5" disk. The reason he is unfortunate is that the Multiface II only recognises drive A - and the 3.5", of course, is drive B. That's one good reason for a device to switch drive B into the drive A position and vice versa, and there are others. My solution is the ABBA modification decribed here. I am pleased to report that all is now well, though he did have to fork out another 30p for a switch. So there you have it: a project to provide a switch to change drives A to B and B to A. Hence ABBA (geddit?). Be honest, you thought I was going to sing a song, didn't you? (If you even try, Craven, you're out- ed.)
Take a chance on me Because the CPC never expected to have to perform this change, we are forced to get inside the machine to make two cuts and a few connections. Chapter 7, page 40 of the computer manual shows the pinouts of the Drive B socket. The only difference between these connections and those of drive A is pin 23 - Drive Select 1 (DS1) which is not fed to drive A. Similarly drive A's Drive Select 0 (DSO) is not fed to drive B. The rest of the connections are fed to, and operate on, both drives simultaneously. All we are going to do is intercept DSO, direct it to whichever drive we want to be drive A and the opposite with DS1. Then, whenever drive A is accessed by the computer, the drive we have selected to receive DSO is used, and the same with DS1. We need one double pole double throw (DPDT) switch, available at any Tandy or Maplin store; a bit of wire; a sharp knife; a soldering iron; and a supply of anti-squeamish tablets. The switch should be panel mounting so that it can be easily fixed to the computer's casing.
The motherboard diagram doesn't show every jot and tittle but has more than enough to do the job accurately. The ribbon cable diagram represents part of the internal disk drive cable and the red edge is indicated. .The 4th (grey) strand should be cut as indicated, and the end nearest the internal drive [INT] should be connected to the switch as shown. Opposite corners of the switch should be connected together and a wire, taken from the pin marked [EXT], should be soldered to the hole indicated on the motherboard diagram. The existing printed circuit track from that hole should be cut. The centre pins on the switch connect to pin 6 (DSO) and pin 8 (DS1) of IC206. Wires can be soldered straight onto the IC's pins but don't take more than about five seconds with the iron on each pin. And that's all there is to it. Follow the diagrams carefully, eat up all your greens and allow plenty of wire inside the computer to the switch, so that it can be opened freely. •
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