Welsh Wizard Posted November 20, 2011 Share Posted November 20, 2011 Both of my 130 XE's have failed on the keyboard membrain the tracks have cracked , I tried using the the conductive pens but it only last for about a hour or so before they crack some where else or in the same place, so I am looking for a supplier or some one who has some spare membrain matrix sheets. Quote Link to comment Share on other sites More sharing options...
BillC Posted December 12, 2011 Share Posted December 12, 2011 Both of my 130 XE's have failed on the keyboard membrain the tracks have cracked , I tried using the the conductive pens but it only last for about a hour or so before they crack some where else or in the same place, so I am looking for a supplier or some one who has some spare membrain matrix sheets. I know you are probably looking for somewhere closer to home, but the only supplier I know of other than getting one from another XE computer is Best Electronics. They list 2 different replacement mylar membranes on this web-page: http://www.best-elec...a.com/130xe.htm Quote Link to comment Share on other sites More sharing options...
Welsh Wizard Posted December 12, 2011 Author Share Posted December 12, 2011 Cheers Moonsweeper thats the first time I have seen them listed any where. Now to save some money and find out how much to post 2 of them to New Zealand. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted April 2, 2012 Share Posted April 2, 2012 The type of keyboard used is known as a "Low-resistance contact", the resistance being about 1000 ohms or so. As you use the keyboard, the resistance of the contacts tend to go up. For the regular keyboard and the RESET key, this increase in resistance causes no problems. But the console keys (OPTION, SELECT, and START) are read by a different IC, and the change in resistance will eventually keep the console keys from working. (The HELP key is actually read as just another letter key). The fix to the problem is to add just enough resistance in parallel to the key so that it is high enough not to make the computer read the key as pressed, but low enough that when the console key is pressed, the computer will recognize it. The original idea for this fix came from Alan Haskell from the book "Mods, Fixes, and Upgrades" available from Best Electronics, 2021 The lameda, Suite 290, San Jose, Ca.5126. One minor problem with the fix, however - it wouldn't work on the 130XE that was given to me to repair. After several hours of pulling out my hair over this thing, (and anyone who has seen my balding head KNOWS I can't afford to do too much of that!) I determined the problem. The resistor value given - 3000 ohms - was too low, for this machine at least. This value was just slightly above what the computer registered as a key pressed. Any random electrical noise would cause the computer to read the key as pressed, which would cause problems with the BBS program that was being used. A higher resistor value was needed. Theres no "correct" resistor value to use, as it varies between different 130XEs. You may need to do some testing (as I did) to make sure it works properly. What You Need: Soldering Iron and Solder Wire Clippers (3) 4700 Ohm Resistors, 1/4 watt A small Phillips screwdriver Needle-Nosed Pliers How to do it: 1) Unplug all of the wires from the computer. 2) Turn the computer over and remove the four screws that hold the top cover on. 3) Turn the computer back over and THEN take off the top cover. 4) Lift the keyboard up and forward and you should see the ribbon connector at the lower right corner. Gently remove the ribbon from the connector. 5) Remove the screws that hold the motherboard to the lower half of the case. Lift the front part of the motherboard up and then forward to remove it from the case. 6) Straighten the tabs that hold the top and bottom shields on and remove the shields. 7) Turn the board over with the keyboard connector facing to the front. The connector pins are numbered from right to left. Pin #3 is the ground connection, and Pins #21, 22, +23 are the pins for START, SELECT, and OPTION keys, respectively. These are the connections you need to make for the repair. Take the three resistors and solder the wire from one end of one resistor and solder it to the second resistor, at the spot where the wire comes out from the connector, being sure to cover them with a short piece of insulation as well. 9) Check your wiring to be sure that there are no shorts! 10)Use as little solder as possible, and make the connection as fast as you can, using as little heat as possible. Place a short piece of electrical tape under on the board under the resistors, if needed, and press the resistors close to the board. 11)Reassemble the shields and check to see that the resistors are not shorting against the lower shield. 12)Reattach the keyboard to the motherboard, taking care not to bend the ribbon - it WILL crack. It helps to insert one edge first, then carefully work the other edge into the connector. 13)To test the repair, power up the computer and in BASIC type: 10 PRINT PEEK(53279):GOTO 10 and type RUN. You should see a vertical row of 7's. Pressing OPTION will give you 3's. SELECT will give you 5's and START will give you 6's. The value should not change while any one key is held down. This should return the normal function of the console keys. Special Note for Techs: You can use the following method to determine the exact resistor value that you need. It might save you time and aggrivation: What you need (in addition): Multitester (digital best) 10K Multiturn Potentiometer Some short pieces of thin wire This should be done between steps #4 and #5 of the above procedure: A) Connect one short piece of wire to the center pin of the pot, the other to one of the other pins. B) Solder the free end of one wire to the ground pin (Pin 3). These connections will only be temporary. Solder the other free end to one of the console key Pins (21,22, or 23). C) Adjust the pot for maximum resistance. D) Reconnect the power and monitor. Reconnect the keyboard. Turn on the computer with the option key pressed - you should get the diagnostic screen. Select the KEYBOARD TEST and hit START. E) Adjust the pot until the tone just starts to sound intermittently. Measure the resistance by connecting the probes to the center pin and the unused pin on the pot. Subtract the measured value from the rated value of the pot to get the proper value. Record it. F) Adjust it again until the tone sounds continuously. Record the value the same way as in step E. G) Turn the computer off, and disconnect the cables and the keyboard. Unsolder the wires from the keyboard connector. H) The proper resistor value to use will be the closest value that is both HIGHER than the highest value recorded, but around DOUBLE the lower value. The resistors you will use will probably be between 3000 and 5000 ohms. Continue on to step #5 as above. I dug this up out of an old BBS..... and it has solved all but one out 20+ supposedly broken trace mylars I have been confronted with... if you do cause a crack it is normally on the short strip from the keyboard to the main board I just paint it and put it in when the traced parts are still damp... if you make the the trace to thick or put it in while completely dried when it bends it will crack again ... less is more! 3 Quote Link to comment Share on other sites More sharing options...
+Larry Posted December 7, 2012 Share Posted December 7, 2012 Thanks for posting/linking this. Missed it before -- really interesting! -Larry Quote Link to comment Share on other sites More sharing options...
Simius Posted December 7, 2012 Share Posted December 7, 2012 There is an easier way to fix the consol problem: 1 Quote Link to comment Share on other sites More sharing options...
ultrasteve Posted January 26, 2017 Share Posted January 26, 2017 The type of keyboard used is known as a "Low-resistance contact", the resistance being about 1000 ohms or so. As you use the keyboard, the resistance of the contacts tend to go up. For the regular keyboard and the RESET key, this increase in resistance causes no problems. But the console keys (OPTION, SELECT, and START) are read by a different IC, and the change in resistance will eventually keep the console keys from working. (The HELP key is actually read as just another letter key). The fix to the problem is to add just enough resistance in parallel to the key so that it is high enough not to make the computer read the key as pressed, but low enough that when the console key is pressed, the computer will recognize it. The original idea for this fix came from Alan Haskell from the book "Mods, Fixes, and Upgrades" available from Best Electronics, 2021 The lameda, Suite 290, San Jose, Ca.5126. One minor problem with the fix, however - it wouldn't work on the 130XE that was given to me to repair. After several hours of pulling out my hair over this thing, (and anyone who has seen my balding head KNOWS I can't afford to do too much of that!) I determined the problem. The resistor value given - 3000 ohms - was too low, for this machine at least. This value was just slightly above what the computer registered as a key pressed. Any random electrical noise would cause the computer to read the key as pressed, which would cause problems with the BBS program that was being used. A higher resistor value was needed. Theres no "correct" resistor value to use, as it varies between different 130XEs. You may need to do some testing (as I did) to make sure it works properly. What You Need: Soldering Iron and Solder Wire Clippers (3) 4700 Ohm Resistors, 1/4 watt A small Phillips screwdriver Needle-Nosed Pliers How to do it: 1) Unplug all of the wires from the computer. 2) Turn the computer over and remove the four screws that hold the top cover on. 3) Turn the computer back over and THEN take off the top cover. 4) Lift the keyboard up and forward and you should see the ribbon connector at the lower right corner. Gently remove the ribbon from the connector. 5) Remove the screws that hold the motherboard to the lower half of the case. Lift the front part of the motherboard up and then forward to remove it from the case. 6) Straighten the tabs that hold the top and bottom shields on and remove the shields. 7) Turn the board over with the keyboard connector facing to the front. The connector pins are numbered from right to left. Pin #3 is the ground connection, and Pins #21, 22, +23 are the pins for START, SELECT, and OPTION keys, respectively. These are the connections you need to make for the repair. Take the three resistors and solder the wire from one end of one resistor and solder it to the second resistor, at the spot where the wire comes out from the connector, being sure to cover them with a short piece of insulation as well. 9) Check your wiring to be sure that there are no shorts! 10)Use as little solder as possible, and make the connection as fast as you can, using as little heat as possible. Place a short piece of electrical tape under on the board under the resistors, if needed, and press the resistors close to the board. 11)Reassemble the shields and check to see that the resistors are not shorting against the lower shield. 12)Reattach the keyboard to the motherboard, taking care not to bend the ribbon - it WILL crack. It helps to insert one edge first, then carefully work the other edge into the connector. 13)To test the repair, power up the computer and in BASIC type: 10 PRINT PEEK(53279):GOTO 10 and type RUN. You should see a vertical row of 7's. Pressing OPTION will give you 3's. SELECT will give you 5's and START will give you 6's. The value should not change while any one key is held down. This should return the normal function of the console keys. Special Note for Techs: You can use the following method to determine the exact resistor value that you need. It might save you time and aggrivation: What you need (in addition): Multitester (digital best) 10K Multiturn Potentiometer Some short pieces of thin wire This should be done between steps #4 and #5 of the above procedure: A) Connect one short piece of wire to the center pin of the pot, the other to one of the other pins. B) Solder the free end of one wire to the ground pin (Pin 3). These connections will only be temporary. Solder the other free end to one of the console key Pins (21,22, or 23). C) Adjust the pot for maximum resistance. D) Reconnect the power and monitor. Reconnect the keyboard. Turn on the computer with the option key pressed - you should get the diagnostic screen. Select the KEYBOARD TEST and hit START. E) Adjust the pot until the tone just starts to sound intermittently. Measure the resistance by connecting the probes to the center pin and the unused pin on the pot. Subtract the measured value from the rated value of the pot to get the proper value. Record it. F) Adjust it again until the tone sounds continuously. Record the value the same way as in step E. G) Turn the computer off, and disconnect the cables and the keyboard. Unsolder the wires from the keyboard connector. H) The proper resistor value to use will be the closest value that is both HIGHER than the highest value recorded, but around DOUBLE the lower value. The resistors you will use will probably be between 3000 and 5000 ohms. Continue on to step #5 as above. I dug this up out of an old BBS..... and it has solved all but one out 20+ supposedly broken trace mylars I have been confronted with... if you do cause a crack it is normally on the short strip from the keyboard to the main board I just paint it and put it in when the traced parts are still damp... if you make the the trace to thick or put it in while completely dried when it bends it will crack again ... less is more! Great info, thanks! Any chance of a picture of a completed fix so that it's obvious to not-so-techy people like me please? Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted October 9, 2019 Share Posted October 9, 2019 On 1/26/2017 at 7:34 AM, ultrasteve said: Great info, thanks! Any chance of a picture of a completed fix so that it's obvious to not-so-techy people like me please? Pictures of 2 completed implementations are now over in this topic: 2 Quote Link to comment Share on other sites More sharing options...
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