pulsar calculator repair

[birox]

Hi,i'm a new member,and i love led watch like all of you. I've bought a pulsar calculator,first series.The watch work perfectly,but the 0 key for activate the calc mode is too hard. I think the keypad need a good contact cleanb service. I don't know exacly how remove the module from the case. I see three little screws on the module border and i don't know if for remove it from the case i must unscrew it or if the screws hold only inner parts of module, for example.
Someone can suggest something to me? Thanks from Italy.
Antonello

[bruce wegmann]

The three little screws hold in place three equally small sheet metal tabs which pivot in and out of narrow slots milled into the inside of the case wall [if the module has never required previous repair, they will be covered in a drop of clear silicone]. All three must be swung aside before the module can be removed [it lifts out as a single unit]. Getting into the keyboard is an entirely different matter. Activation of various functions is accomplished by a conductive spot on one layer being pressed across lines on the primary circuit board. I can't think of any safe or reliable way of prying your way into this assembly and have a better-than-even chance of improving things [there are SO many ways to make things worse!]. Also, this is a not a task I would suggest as a first-time-out exercise [even Time Computer required any Calculator with problems be returned to the main Service Center in Lancaster]. The wire bonds in the display are open and unprotected, and the module can be effectively destroyed by setting it face-down on a firm surface. Unless you lose the calculator completely, I would learn to live with a slightly cranky keyboard...

[retroleds]

Welcome birox! When you say it pushes hard, maybe you mean it sticks, as opposed to requires hard pushing to make contact? If that is the case you can take a soft toothbrush, dip it iin some isopropyl(rubbing alcoho, higher % of alcohol the better, less waterl) and gently scrub the keypad - hold the watch face down if you are really worried. There is a rubber membrane inside to keep water that seeps around the buttons from getting to the module, but that may or may not have failed, so don't flood the thing. You can use a pointed wooden toothpick to clean around a sticky button from the outside, as it won't scratch or gouge the metal. Finally, you can try a very small amount of an electrical grade lubricant that says it won't harm rubber or plastic - again, trying to avoid any damage to the rubber membrane inside. My current favorite is "2-26" electrical lubricant, found at Home Depots in the USA.

If you want to see the inside of the calc before messing with it, take a look here http://www.dwf.nu/Gallery/thumbnails.php?album=21

You do have to avoid even the slightest contact with the display area, as there are super fine wires "wire bonds" that are about 1/3 the thickness of a hair going to each LED segment - repair is possible, but with a degree of failure, even with the best of equipment. The rubber membrane can be peeled out of the bottom of the case, but you don't want to tear the thing. It gets sealed around the edges with silicone. And regarding your module hold down screws - some have 4, others have 3. You will have to remove a thin line of silicone around the entire edge of most calc. modules. Grab the module by the plastic between the battery ports with smallpliers and pull gently, wiggling, after assuring you have the hold-down clips out of the way. Good luck - but really, try the cleaning first.

[birox]

Thanks to all for the answer.
i've a good experience with micro-mainboard (i've destroyed many led watch when i was teenager...now i'm sadly run to 50's then i've more patience...),usually i repair some standard led watch then when i've some hour free i try to disasseble it. Many many thanks again, ciao.

[birox]

UPDATE: successfull operation: i've clean the keys only(some previous owner have clean the metal with some polish product, then the keys have deposit of it that "brake" movements ...) Ciao and an HELLO to Ed...