04-26-2003, 02:39 PM
why did hp change from a plain plastic back to one with an aluminum plate in 1984. was this some orwellian thing?
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71b history question
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04-27-2003, 03:21 AM
I'm guessing here
Most changes are driven by either customer satisfaction The Metal back is there (at least - maybe other things as well) as part of the ESD sandwich. I read in some previous material that they ZAP(ed) something like 15kV through calcs and they have(had) to survive that (in running mode), undisrupted. However the metal is vulnerable for scratches and dings more than the plastic and the process of mounting and miniscrewfixing is cumbersome (some of us tried loosing (and hopefully finding) some of the nuts, bolts (if they are called that at 1mm) spacers etc.) imagine the repaircenter guys. I have not looked in a plastic back, but I would expect to find a sheet against the inside bottom of the 71 replacing the metal. So in short - I assume cost reduction and cosmetics. Kim
04-27-2003, 02:51 PM
The plastic pack is much easier to assemble and repair. There is a metalic connection strip, similar to a what's in the 41 that make the two halves go together very easily. In the metal back versions there is a flex circuit that is soldered to both halves. This is very costly and makes repir difficult. Now, why metal vs plastic. Again, I think it is much cheaper to build. The metal back version has 3 additional screws that make electrical contact between the back and the insides. BTW, I have owned over 60 of these and the only ones I have ever fail or are the metal back versions. Maybe a quirk but I have a box of bad metal back versions and none that are plastic. The flex cable often gets corrosion, for some reason.
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