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8-bit Software Disc Magazine (c) Duncan Webster DEC 1991 Issue 17 December 1991 Tech Tips Issue 4 One of the BBC's main bottlenecks was the rather poor quality speaker built into the machine. Beleive it or not, a larger speaker can certainly make a lot of difference and can make the Model B sound much better. This article by E.M. Clark explains the steps that need to be followed in order to fit a large speaker to your model B. *** IMPORTANT *** No responsability is accepted by the author or 8-bit Software for any damage caused to machines whilst following the steps in this article. Provided you have a little pre-knowledge of the inside of a BBC B and are reasonably competent with electronics, then this upgrade should not be too difficult. No Modifications should be attempted if you do not possess the necessary skill/knowledge for such an upgrade. ______________________________________________________________________ ENHANCING THE SOUND OF YOUR MODEL B Now that the shine and sparkle has vanished on this machine, perhaps this simple modification will hopefully be of use to someone...or two! First of all you will need about 1 Metre of screened cable, with both ends bared. Solder one end to a 3.5mm jack plug, the screening going to the body of the plug and the centre core to the tip. Solder the other end to a 3 or 8ohm speaker, you can solder the wires any way round. A 4 or 5 inch speaker is ideal, as long as it is not another squeaky little toy as in the Beeb! Next, make sure the machine is switched off, or better still, disconnect it from the mains. Remove the top cover of the Beeb, then remove the keyboard, after first unplugging it from the motherboard. You will notice a small plug with wires attached going to the speaker, unplug it, and fold it back. If you have another socket of this type then solder two wires to it, each about 18" long, if you haven't got one, then cut the wires on the existing socket leaving as much wire as possible. Extend the length of these wires so that they reach the back of the beeb, with a bit to spare. Don't forget to insulate the joints. Next drill a hole in the back of the machine near to the ADC socket, and fit a 3.5mm jack socket, solder the two wires to the socket. Making sure there are no short circuits, switch on the beeb and check for sound output. The sound output level can be adjusted by the small vertical potentiometer VR1 close to the speaker plug, which is PL15. Once the sound level is to your liking, switch off the machine and replace keyboard and keyboard connector, and then the top cover. This little mod will give you better quality output. You can try this mod out before finally drilling the hole in the case if you wish, if you "float" the jack plug and socket and check to see if you are satisfied before making it a permanent job. Don't forget to make a drawing of the original wiring in case you want to return to it. By inserting another jack plug into the speaker output socket but this time connecting it to an amplifier, will give even greater output ... providing you have an impedance match,or in other words, it is compatible. This completes the article, if you have found it useful and would like other articles in the future then please let Duncan know and thereby me. It should be stressed again that this article is directed at those members who are confident enough and knowledgeable enough to make the necessary alterations to the computer. If you are in any doubt then seek assistance from someone who is comptent enough to undertake the job properly. E.M. Clark K24. ______________________________________________________________________ QUESTIONS FOR FUTURE TECH TIPS User 2GJ: Roger Pashby Does anybody know what the command is to switch CAPS LOCK on and off. I am sure that it is a simple *FX call or a VDU command, but i'll be blowed if I can find it anywhere. I want to include a password system for a menu I am building. I want the user to be able to input his/her own password upon first booting up and then then menu will auto save with the password built in, so that in future it will request that password or hard break. The file will also need to be protected so that is cannot be read and be protected. Anybody suggest a routine?