=<>=<>=¢¢ KEYBOARD FIX¢¢ This article has been taken from Z*MAG¢ Atari on-line newsletter. It is a good¢ article on fixing keyboards, even¢ though it can't solve all problems.¢ File was transferred by Mike¢ Blenkiron, and tidied by Dean¢ Garraghty and reprinted by THE OL'¢ HACKERS, A.U.G., Inc.¢¢ ----------------------¢¢ This is probably one of my last¢ original articles from me for a while,¢ but I will try to bring you some of¢ the best fixes, modifications, and¢ other projects of other authors in the¢ coming months. In this article¢ however, I will try to give a little¢ help on fixing one of the more common¢ breakdowns, the keyboard. I'm sure¢ quite a few of you have an Atari in¢ the closet with a keyboard that has¢ gone belly-up in one way or another. ¢ You would like to put that machine to¢ use again, or would like to sell it¢ for the best price as a working¢ computer, so let's dig right in.¢¢ The 400's membrane keyboard was a joke¢ from the git-go. The only solution¢ there is replacement, and a lot of¢ people replaced them with third party¢ keyboards. Since there were so many¢ manufacturers, I can't even begin to¢ cover them all here.¢¢ With the 800's, as well as the 800XL,¢ there were more than one design of¢ keyboards, by far the most durable of¢ which was the full stroke, contact-¢ switch type. Stackpole was one of the¢ major manufacturers here. While I'm¢ not sure about what percentage of¢ 800's used this type, not many of the¢ 800XL's had them. If you should¢ happen to have an 800 or 800XL with a¢ Stackpole keyboard, then you should¢ have very little if any problems with¢ it. If you lose function of a key¢ here, a nice bath with a good tuner¢ cleaner will take care of even the¢ nastiest keys. If that doesn't work,¢ then the keyswitch can be replaced.¢¢ The other was the printed circuit¢ contact sheet, where conductive paint¢ traces were silkscreened onto plastic¢ sheets. My 800 is one of these,¢ manufactured by Mitsumi, and a lot of¢ the 800XL's were made by Chelco. Here¢ you must exercise a little more¢ caution. DO NOT use any solvent type¢ cleaner or you will wash the traces¢ right off. The only thing you can use¢ here is a little water and a soft¢ cloth. Even alcohol will discolor the¢ traces and raise the resistance. If a¢ trace is broken, a little dab of¢ conductive paint, available at any¢ electronic supply store, will fix it¢ up nicely. If the key still doesn't¢ work, try giving the spring that¢ presses against that contact a little¢ stretch. Be careful here, as it is¢ easy to go too far and have the key¢ stick on all the time. Remember, it is¢ easier to stretch a spring than it is¢ to shorten it, (cutting it is "NOT" an¢ acceptable alternative!!). If the¢ problem is a key sticking on all the¢ time, try it with the pressure spring¢ removed. If it stops repeating, then¢ shorten the pressure spring by¢ squeezing it down with gentle¢ pressure. If it still sticks, then¢ take the separator sheet (the one with¢ all the holes in it), and add a piece¢ of scotch tape over the corresponding¢ hole, and cut out the tape where it¢ covers the hole. Don't use masking¢ tape or anything like that, as it is¢ too thick. You should never use more¢ than two layers of scotch tape for¢ this type of repair. If it still¢ sticks after two, then replace the¢ keyboard or use the computer for¢ parts. There are quite a few 800XL's¢ floating around that can be had for a¢ more-than-reasonable price, and you¢ should be able to find one with a¢ working keyboard.¢¢ The 130XE was a radical departure from¢ the others, in that it used only a ¢ single sheet of plastic, with a¢ contact on the bottom of the keyshafts¢ bridging two contacts on the sheet. ¢ Here if cleaning doesn't help, save¢ yourself a lot of aggravation and¢ replace the keyboard.¢¢ If you've found everything to be fine¢ and dandy with the keyboard itself,¢ but you don't have function of a group¢ of keys, check the ribbon connector¢ where the keyboard connects to the¢ computer. There may be a bad¢ connection. On the 800 this shouldn't¢ happen, as this is a full plastic-¢ bodied 18-pin connector. On the¢ 800XL, the ribbon is merely an¢ extension of the silk-screened sheet¢ that slips into a connector on the¢ main board. If part of the conductive¢ paint has been scrapped away, you can¢ reach fresh trace by trimming down the¢ ribbon a little. If you find yourself¢ having to go too far, then replace the¢ keyboard.¢¢ Sometimes the problem is on the main¢ board itself. The keyboard is read by¢ two 4051 decoders and fed into the¢ POKEY chip. Try swapping out the¢ chips, one at a time, and eventually¢ the keyboard should come back to life. ¢ If not, then there is a more serious¢ problem that requires professional¢ attention.¢¢ Hopefully, I have given you enough¢ information here to enable you to do¢ some of your own keyboard repairs and¢ save a little money.¢¢ *=end=*¢
