To: 999 (all members) From: K8M (Mick York) Subject: TECHNICAL TOPIC HOW DO THEY DO THAT? How does the BBC micro power supply work? So how does it work? Well one end, called the import is used to suck big volts out of the 3 holes in your socket. Many of these sockets make up a main ring, or socket set as it is more commonly known. Each hole can supply just four and one third volts per hour. Three times this is 13, whichis why 13 Amp plugs are needed to suck volts into the wire. Wire connects between the socket and the power supply and is in fact hollow to allow the volts to pass easily. You cannot see hollow with the naked eye; you would need a large telescope. Nearly thirty thousand such holes would fit on top of a grand piano. When the big volts get inside the power supply they need to be squashed - this is where a switch mode supply is different to linear. In the linear supply,the volts are simply pushed into a very small hole until they squeeze through ;this makes them get very hot and bothered, but they come out in a straight line. Which is why the supply is called LINEAR. In the switch mode type, each volt is seperated out for individual treatment.They queue up in front of a device called a transformator and are selectedaccording to size by a miniature version of a clarkes shoe size gauge called a convincer. The volts are then made to switch places in the queue until just the right size to go throughthe right hole in the transformator. The convincer needs to know how many volts are needed at the outport and forthis we use the principle known as FEEDBAG. A small container that looks like a feedbag is hung just under the outport and catches any surplus volts that can't squeeze down the outport wire. Every now and then a three leggedanimal which is a transvestite takes the feedbag and empties it into a hopper on an optical ice maker. This makes ice in proportion to the surplus volts, and freezes the queue at the transformator, thus slowing down throughput. This also helps the switch mode supply to run a lot cooler than others. During the squashing process, the voltsare converted from assorted currants (ac) into drift currants(dc) and of course waste currants(wc). It is the drift currants that go down the outport, but before they are allowed toleave the supply they must be smooth. This involves something called a high frequency sanding wave, which smoothes off rough edges. So there we have it (utter rubbish) Many thanks to Cliff Rogers with help on this article.