Dave, Well, best of luck ...
I'm glad to read that you are, at least, thinking of NOT going with a replica of the original membrane ... BTW. Just as many want to hold to their notion that the material selection, alone, is the problem, I will maintain my belief that if the tails were not located in proximity of the heatsink that the problem of premature aging would probably not have occurred. BTW2. The fact that the chimney effect draws smoke out the vents behind the heatsink MEANS that is the hottest location inside the case. The fact that a peripheral is usually plugged into the expansion slot means that the optimal air flow that might cool the tails just doesn't occur. Think about it. As noted by almost EVERYONE, the failure IS, indeed, usually at the bend in the membrane tails which is adjacent to the heatsink when the upper half of the case with the keyboard is in place above the motherboard on MY QLs rather than being at the "opposite (?) end" as you seem to suggest! Al On Fri, 8 Mar 2002 14:42:42 +0000 (GMT) Dave <[EMAIL PROTECTED]> writes: > > > On Fri, 8 Mar 2002, Al Feng wrote: > > > Speculation about the material used in the QL's membranes by > Sinclair or > > otherwise seems futile. > > I disagree. Here's why. > > They fail. We have to produce something that does the same function. > We > don't want it to fail the same way. > > > It is worth noting, IMO, that the reason that the membranes have > failed > > in the past, and will probably fail in the future in a standard > QL > > configuration IS singularly BECAUSE of the proximity to the > heatsink. > > The heatsink is at the opposite end of the QL, and if you put smoke > into a > QL you'll see it is drawn in at the expansion end, drifts slowly to > the > heatsink end, then accelerates rapidly and comes out of the grille > at the > back of the heatsink. > > > Think about it. > > I have, for a couple of weeks now, full time. :o) > > > As long as the standard PS configuration is used, you are baking > the > > tails. The rest of the keyboard membrane does not appear to > suffer from > > the problem of becoming brittle. > > The baking is what causes the pthalates to evaporate. The heat comes > from > components on the board. > > > If you want to make a BETTER *membrane*, then get hold of a > TS-2068 and > > see how Timex made their keyboard -- printed circuit, carbon pads > to > > close the circuit, ribbon wire tails attached to a connector. > > These are approx 3mm deeper than the current design. I am > experimenting > with them. They work very well and are durable. I'm just waiting for > a > better selection of expansion cards to check clearances, etc... > > > Worrying about the pressure needed to actuate a "key" is a silly > exercise > > if you are simply trying to create a replica of the original > membrane > > because your keyboard membrane's tails will inevitably suffer the > same > > fate which the original membranes experienced ... > > Worrying about the key pressure is very important. Part of the total > key > pressure required comes from the inertia of the keycap, to > accelerate it > down (about 5%), part comes from the rubber bubble mat (about 60%), > and > part comes from the membrane itself (about 35%). If it requires 1 > unit of > pressure to press the key, and I produce a membrane that requires, > say, > double the pressure to operate, it requires a pressure of 1.35 > units. This > different will be enough to throw off most fast typists, and if > you've > been using a keyboard for 18 years, the last thing you want is for > its > characteristics to change. It's a small bit of effort to make a > permanent > quality product that will last forever and not have any negative > side > effects. > > After experimenting with the QL I have here, and checking > specifications > for a type of kbd that uses the exact same construction as the QL > and OPD, > I can report that the force specified is 2-3 Newtons. The force > actually > required increases as the keyboard ages, because the bubblemat and > membrane top layer become slightly stiffer. > > If I am going to invest several thousand dollars in a project, I am > going > to make sure I understand 100% all the issues involved with my > designs, > and with the design decisions of the original membrane. Only by > understanding the specifications and requirements for performance > will I > make something that is *perfect* :o) > > If I can see a way to make this work, every membrane will be stamped > with > a "Born on" date, so people can tell how old it is. > > Dave > ql.spodmail.com > > > --- On Fri, 8 Mar 2002 14:42:42 +0000 (GMT) Dave <[EMAIL PROTECTED]> writes: > > > On Fri, 8 Mar 2002, Al Feng wrote: > > > Speculation about the material used in the QL's membranes by > Sinclair or > > otherwise seems futile. > > I disagree. Here's why. > > They fail. We have to produce something that does the same function. > We > don't want it to fail the same way. > > > It is worth noting, IMO, that the reason that the membranes have > failed > > in the past, and will probably fail in the future in a standard > QL > > configuration IS singularly BECAUSE of the proximity to the > heatsink. > > The heatsink is at the opposite end of the QL, and if you put smoke > into a > QL you'll see it is drawn in at the expansion end, drifts slowly to > the > heatsink end, then accelerates rapidly and comes out of the grille > at the > back of the heatsink. > > > Think about it. > > I have, for a couple of weeks now, full time. :o) > > > As long as the standard PS configuration is used, you are baking > the > > tails. The rest of the keyboard membrane does not appear to > suffer from > > the problem of becoming brittle. > > The baking is what causes the pthalates to evaporate. The heat comes > from > components on the board. > > > If you want to make a BETTER *membrane*, then get hold of a > TS-2068 and > > see how Timex made their keyboard -- printed circuit, carbon pads > to > > close the circuit, ribbon wire tails attached to a connector. > > These are approx 3mm deeper than the current design. I am > experimenting > with them. They work very well and are durable. I'm just waiting for > a > better selection of expansion cards to check clearances, etc... > > > Worrying about the pressure needed to actuate a "key" is a silly > exercise > > if you are simply trying to create a replica of the original > membrane > > because your keyboard membrane's tails will inevitably suffer the > same > > fate which the original membranes experienced ... > > Worrying about the key pressure is very important. Part of the total > key > pressure required comes from the inertia of the keycap, to > accelerate it > down (about 5%), part comes from the rubber bubble mat (about 60%), > and > part comes from the membrane itself (about 35%). If it requires 1 > unit of > pressure to press the key, and I produce a membrane that requires, > say, > double the pressure to operate, it requires a pressure of 1.35 > units. This > different will be enough to throw off most fast typists, and if > you've > been using a keyboard for 18 years, the last thing you want is for > its > characteristics to change. It's a small bit of effort to make a > permanent > quality product that will last forever and not have any negative > side > effects. > > After experimenting with the QL I have here, and checking > specifications > for a type of kbd that uses the exact same construction as the QL > and OPD, > I can report that the force specified is 2-3 Newtons. The force > actually > required increases as the keyboard ages, because the bubblemat and > membrane top layer become slightly stiffer. > > If I am going to invest several thousand dollars in a project, I am > going > to make sure I understand 100% all the issues involved with my > designs, > and with the design decisions of the original membrane. Only by > understanding the specifications and requirements for performance > will I > make something that is *perfect* :o) > > If I can see a way to make this work, every membrane will be stamped > with > a "Born on" date, so people can tell how old it is. > > Dave > ql.spodmail.com > > > ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/.
