curzon@troa01.dec.com (12/20/88)
SUPPLIED BYT THE CHAOS BBS (517) 371-1106 XE CONSOLE KEY FIX... ... that really works. I found that I was not alone when I started having trouble getting my console keys to work on the ATARI 130XE the CHAOS club used for its BBS. It seems that very many of the machines develop this problem. I asked around and found several others that had done as I did, opened the keyboard and cleaned the button contacts, only to get good results for a week or so before losing them again. I then received a couple reprints of articles suggesting hardware fixes. I tried a couple that did not work, but one that worked the best came from Alan Haskell (printed in the SBACE GAZETTE, April/May '86). Heres how, with a small modification to save you the trouble I made for myself trying his recommended installation. You will need a small phillips head screwdriver, needle nose pliers, a small soldering iron, and three 3k (3,000 ohm) resistors. Quarter-watt rating is plenty, in fact, the smaller the resistors are physically, the better. 1. Turn over the XE computer and remove the 4 screwss that hold it together. Turn the computer over again and remove the top half of the case. 2. Lift out the keyboard and gently pull the ribbon out of its connector. DO NOT OPEN THE KEYBOARD as cleaning internally will not help, and you may damage the carbon tracks on the baking sheet inside. 3. Remove the motherboard from the lower half of the case by removing the phillips screws holding it down. 4. Remove the top and bottom metal sheilds from the board by carefully straghtening the bent tabs that go through the board. 5. Observe the top and underside of the connector you pulled the keyboard ribbon out of. As seen from the top as you would look at the computer normally, there are 24 connections, with connection #1 at te left and #24 at the right. Connection #3 (from the left) is the ground connection. The last 4, #21, #22, #23, #24 are the START, SELECT, OPTION, and RESET connections. When a connection is made from these points to the ground, the computer will know one or several of the keys are being pushed. Due to a design problem, the console keys have a bit too much resistance to always register even when you really lean on them. So, we will install the three resitors between the connections and ground so as to "leak" a bit more ground signal to the computer. That way, not nearly so good a connection is required by the actual keys when pressed. 6. Identify the proper pins on the bottom side of the circuit board. We will install the resitors under the board. 7. Solder one end of all three resitors together. Then connect this common end to the ground connection (pin 3). Then solder the free end of the resiters, one each, to pins 21, 22, and 23. (The reset system never seems affected, nor any other keys.) 8. Be certain that the wires on the resistors do not touch each other nor any other circuitry! Use as little solder and as short a heating time as possible. Tape the resitors to prevent shorting if needed, and press them close to the circuitboard. 9. Reassemble the shields to the board, bending back the tabs to hold it all together. Look inside to be sure the resitors do not touch the lower shield. 10. Complete the re-assembly, taking extra care not to stress or insert the keyboard ribbon too many times. The spring contacts bend easily, and the conductive coating on the ribbon, if scratched through, will cause the keyboard to be useless. Don't worry too much, thats hard to do if you are careful. (The original mod suggested pressing the resistor leads into the connector so as to make it solder-free and simpler.... but that "simplicity" ruined my connector and made hour more work! Solder it!) 11. Test the repair. Power up the machine and type in this one line basic program: 10 PRINT PEEK(53279):GOTO 10 Then type RUN. You will see a row of 7's down your screen. Push OPTION. They should turn to 3's. SELECT will give you 5's, and starts will give you 6's. Combinations will give other numbers from ) to 7. If each key responds, you have finished the repair. This has permanently fixed the problem on dozens of XE's. It has restored my keys to "feather touch" after a long siege of having to boot 5 or 6 times mashing the OPTION key trying to get a boot without BASIC. It WILL work for you. John Nagy, SYSOP of the CHAOS BBS (517) 371-1106