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CPC 464 Plus Memory Upgrade (1/2) (Amstrad Action) | CPC 464 Plus Memory Upgrade (2/2) (Amstrad Action) |
If all went well last month, you should now have a 464 Plus with an extra 64k of memory. Warm up that soldering iron again because here comes Phil Craven with details of how to fit a disc interface to your 464 Plus. Last month we saw how to add the extra 64k of memory to the 464 Plus computer to put it on a par with the memory of 6128 Plus. I trust we all performed the operation without a hitch. This month we're going the rest of the way to turning your 464 Plus into a 6128 Plus, or what I like to call a '464 Super Plus', by adding the disc drive interface and disc drive. I call it the 'Super Plus' because, when complete, it is actually better than the 6128 Plus in that it has everything that the 6128 Plus has, and it has a tape deck. 6128 Plus owners get the opportunity to strike back next month when we'll show them how to add the tape in/out with remote facility. In case you missed last month's issue, the 464 Plus and the 6128 Plus have identical circuit boards. The difference between them is that the 6128 Plus has its extra 64k and disc interface components fitted where the 464 Plus has tracks and empty holes and the 464 Plus has its tape components fitted where the 6128 Plus has tracks and empty holes. Since they both have the same system ROM, fitting the correct components into the correct holes quite literally turns one model into the other. The only differences then being that one has its tape deck built in and its drive on the outside and the other has the opposite. It's possible to add an extra 64k and disc interface to the outside of the 464 Plus but the beauty of putting them onto the computer's circuit board, where Amstrad designed them to be, is that they're neat, out of sight and a heck of a lot cheaper! The plug-on 64k costs £39.95 to buy, and that's a discounted price, but we did it last month for around a tenner. The plug-on disc interface costs around £90 but we're going to do it for a mere £25. Chips with everything Speaking of which... When researching this project I found that CPC of Preston, Amstrad's parts distributor, is the only source in Europe for one of the required chips, the SED9420CAC. For a user to buy it there would cost almost £28 plus delivery! And that's just one chip. Fortunately, ifs available as part of Avatar's disc interface kit and Avatar have agreed to supply the whole kit of parts for this project at £25, including carriage. This is lower than their normal kit price but it won't include their normal bells and whistles (instructions, etc.) so, when ordering, be sure to specify that it's the kit for the Amstrad Action project or you might be charged an extra fiver. Look before you leap Before you rush to buy the kit, have a look at what you'll need to do. If you think you can do it, then go ahead. If not, but you still want it done, see Avatar's ad. So let's get to it. Open the box... Separate the computer from the monitor and remove all peripherals, including the cartridge and tape. Turn it over and take out all six screws. Notice the three catches, one at the front and one on each side. Turn the computer the right way up again and undo the catches by pulling the front one towards you and the side ones outwards. Open the tape cover (press 'EJECT') and the computer's top will fold back and away from the bottom. It is still connected to the bottom so don't whip it away. ...and take a look inside At this point, pause a while, study and compare the diagrams with the circuit board, read through this project and become fully familiar with what you will need to do. If you think it is beyond your capability, now is the time to close up the computer. If you've bought the kit, contact Avatar who will help.
Fig.1 represents the whole of the circuit board with a few major components shown. The bold and shaded components are the five chips (ICs 3 to 7), the connector (JD04), the wire link and the various resistors and capacitors that need to be fitted. You can see the holes in your actual circuit board for each of them. If you look closely, you can see that all the holes have been filled with solder which needs to be removed before the components can be soldered into place. If there's a boring part to this project, it's removing the solder but, when done, the project is almost finished. Don't make the mistake of trying to solder the IC sockets into place without first removing the solder. I've seen it done and although it looked alright the project didn't work. That method can be done with the resistors and capacitors but not with the chips. Maplin and Tandy sell low cost solder suckers. Fig.2 shows the main components to be fitted in actual size and Fig.3 shows the detail of the JD04 disc drive connector. Remove the board Disconnect the two pair of wires that join the computer's top to the circuit board. Notice that they are colour coded. The yellow wires with the black socket go onto the black plug and the blue ones onto the blue plug. You'll need to reconnect them correctly when the job is done. Pull the tape connector and keyboard's 'film' connectors up to remove them from the circuit board and take out the three screws that hold the board to the base - see Fig.1. Remove the board from the base but take care not to handle any components. It is rare these days to zap components by the body's static electricity but it is better to err on the side of caution. In choosing a suitable place to work, remember that the pins on the underside of the circuit board scratch polished surfaces. You have been warned. Remove the solder Suck the solder from all the required holes. If you haven't done this before it will take you a few holes to get used to but then it's easy. Hold the sucker poised close to a hole and, with your soldering iron, melt the solder inside the hole. When melted, quickly move the sucker over the hole and press the sucker's button. Most holes will clear in one suck but don't waste time redoing those that don't. Wait until you've done all the holes of one chip before going back to the ones that didn't clear and then fill them with solder before sucking again. It is easier to clear a hole full of solder than a partially filled hole. If the coil component is in the way of the JD04 holes, pull it away from them. Clear all the holes for IC3, IC4, IC5, IC6, IC7, NR01 and JD04. It is best also to clear the holes for resistors R6, R7, R8, R9f R10, R11 and R12 and capacitors C3, C4, C20,and C22. Capacitors C21 and C23 have a wire already in one hole and can be treated differently.
Fit the IC sockets Solder each of the IC's SOCKETS into place. Push a socket into its holes, turn the board upside down and solder each of its pins. When you're doing this, bend a couple of corner pins over before turning the board upside down to make sure that the socket doesn't slip back through the holes. Don't insert the chips into the sockets just yet. Fit the other components Solder all the CAPACITORS and SINGLE RESISTORS into place. They are of different values so use the parts list to get the right one in the right place but they can be fitted any way round. It doesn't matter which of their pins go into which of their holes. C21 and C23 each have a wire soldered into one of their holes. Rather than remove the wire, solder the capacitors to the underside and bend them flat against the circuit board. Solder the 36 way centronics connector into JD04. It is alright for the coil component to rest on JD04's pins. It looks as though it would conduct electricity but it won't. NR01 is a RESISTOR NETWORK and must be fitted the right way round. It has a dot at one end which must point towards the back of the computer. Fig.1 shows the dot as the black end of NR01. Fig.2 shows it separated by a thin line. It can now be soldered into place. The WIRE LINK is what allows the computer to use a drive A. Without it, only drive B would be recognized. One end solders into the hole in CD04 as shown in Fig.1 and the other end solder directly onto JD04's 5th pin on the top row. JD04 has two rows of angled pins, one above the other. The wire link should be soldered to the top row and to the 5th pin along from the left. Fig.3 shows it in detail. Fit the chips The chips can now be pushed into their sockets. See the parts list to get the right ones into the right sockets. It is very important that they are inserted the right way round. Each chip has either a half moon shaped notch or a corner dot at one end only. That end must be towards the back of the computer as shown in the diagrams. Most chips are supplied with their pins splayed outwards, many will fit straight into a socket but some won't. The quick way to straighten those that don't is to bend a whole row at a time by resting the row on a hard surface, holding the
Just cut a little slot The upgrade is now finished but there's one thing left to do. A slot must be cut out of the top casing for the JD04 connector to poke through. If you look closely at the back of the case, you will see two lines moulded into it. These are exactly where you need to cut so cut down them to about the same depth as the slots for the other connectors. Deeply score a line between the two cuts with a Stanley knife or similar and break off the unwanted bit of casing with a pair of pliers. Use the knife six or eight times to get a deep enough score. Any tidying up that's needed can be done with a file. Put it together again Now you can put the whole thing back together again not forgetting to reconnect the black earth wire from the tape deck as you screw the board onto the base. The copper leaf springs should rest on the underside of the keyboard so, if they have been bent down during the operation, bend them back up again. When the computer is back together, but before the six screws are put back, try to close the tape lid. If it won't close without pushing on the JD04 connector, you will need to cut away part of the plastic on the left side of JD04 to allow the tape lid's lever to move freely.
Is that it, then? That's it. All done. But if you need technical assistance, phone 0274 *****. If the project is done according to the instructions, it will work. However, neither AA, nor Future Publishing, nor the author can accept any liability or responsibility for what a person might do inside the computer in the course of carrying out this project. Disc Drives Now, the 464 Plus is capable of accessing two disc drives. The first should, obviously be the A drive and, for that, you can use any of the three main sizes: 3", 3.5" or 5.25”. Most CPC disc software is only available on 3" discs but 3" drives are difficult to get. 5.25" drives are a bit old hat but the popular 3.5" is widely available. Whether to search for a 3" or go straight for a 3.5" depends entirely on the user. Games players should try to find a 3" but serious users can usually manage with a 3.5". Disc prices should also be considered. 3.5" discs cost a fraction of the price of 3" ones and can hold twice as much data. Whichever size you opt for, be sure to tell your supplier that you want an A drive. Amstrad 3" drives are fine as they are, even if they've been used as B drives, but 3.5" ones are normally dedicated B drives unless specifically altered to be A drives. The 36 way centronics JD04 connector is identical to that used on the 6128 Plus but you need to make sure that your supplier can supply a drive to fit the Plus computer as distinct from the older CPCs which have different connectors. Not only that but you need to make sure that your supplier knows how to put the connector onto the drive's cable for the Plus computer as it is done in an unexpected way. Any disc drive retailer, advertising in AA, knows how to do it. Adding a B drive isn't quite as straight forward since there's only one JD04 connector but it can be done by using a custom-made drive port splitter which would convert the one JD04 connector into two connectors. AA |
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