|Re: Is there anyway to fix Pioneer series key SNAP???|
Message #2 Posted by Randy Sloyer(US) on 1 Dec 2002, 12:26 a.m.,
in response to message #1 by Steve
Are these nasty cracks coming from a newer Indonesian unit? I would bet money on it. I have not seen a early USA or Singapore unit snap. Unless of course you've spilled some soda into the keyboard, but then your calculator would probably not be working as this is the fastest way to disable a pioneer, since the batteries never seem to die :)
Before I tell you I don't have an answer for you, let me tell you what I've seen in dissecting several flavors of pioneers. Perhaps that will get some discussion going and someone may have or come up with a solution. The current keyboards are comprised of 4 identically sized mylar sheets that sit atop a formed metal sheet that is the skeleton of the calculator. The bottom sheet is just a spacer with a hole in each key position, the second layer is a rather novel double sided flexible circuit that is guts of the keyboard. The third is again another swiss cheese spacer sheet. Right under the key is the top and final layer, the dome sheet. The sheet has small domes formed into the mylar onto which a flexible film resistive dot has been printed.
When you press a key, the dome deforms, allowing the resistive dot to collapse through the top spacer layer and contact the conductive sheet below, completing the circuit. When the dome snaps back, you sometimes get a clicking sound. I believe this is present from the beginning and it just will not go away with use. I have a newer 42S that has this annoying habit. I've been banging on it for 6 months now and it has not changed a bit.
I think there are at least two possibilities for the snapping. One is a change to the dome sheet. I've looked at both old and new sheets and they are made of the same 0.005" mylar. I have not measured the force required to deform the domes as I don't have the necessary equipment, but it is possible that the orientation is different in the sheet, requiring higher forces and the equal higher force return, resulting in a snap.
The other is related to dome force, that is, the dampening of the return of the dome. One thing I have noticed in the various units that I have opened is that I believe HP changed the formulation of the case material over the production life-cycle. The early machines had a harder finish, perhaps from a higher styrene content, to the current softer material on the newest machines. This change in material changes the way the keytop rebounds from the dome popping back. The newer, softer material does not dampen the force as well, resulting in the snap of the mylar as it comes back to it's original pre-stressed position. Just hold your finger on the key as it comes up, just a bit, and the snapping should not occur.
Just my 0.02 cents worth. I have several different keyboard mylar sheets in the pioneer parts box and would be happy to post some photos if anyone wants to continue this. I would like to find an answer myself...