=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+¢¢This article has been taken from Z*MAG Atari on-line newsletter. It is a good article on fixing keyboards. File transferred by Mike Blenkiron, and tidied by Dean Garraghty, ENGLAND?? (From his NEWSLETTER #2, with thanks!)¢-----------------------------------¢¢ (Reprinted from the Mid-Florida Atari Computer Club Bulletin)¢by Len Spencer¢¢¢This is probably one of the last articles original to 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 notsure 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 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 your own keyboard repairs and save a little money.¢¢ !|!|!|!|!|!|!|!|!|!|!|!|!|!|!|!|!|
