|Re: HP-42S dead?|
Message #17 Posted by Paul Brogger on 30 Apr 2003, 11:20 a.m.,
in response to message #1 by Mike (Stgt)
Sounds like your next step may be to disassemble the unit, and swap out the PCB for another (from a 17B/BII, 27S or 42S) to try to isolate PCB problems from keyboard/display/connection issues.
It's nice to have a disassembled clean functioning spare -- both keyboard/case/display and PCB -- available for such testing. (I use a 17BII.)
Assuming disassembly goes well, the main things to worry about are scratching the PCB traces when you're twisting the hold-downs, and absolutely minimizing the number of times those twisties are cycled.
These units were not meant to be serviced, and the metal hold-downs (or whatever they should be called) that fasten the PCB to the display bezel will only stand being twisted back & forth a few times (maybe a half-dozen if you're lucky) before metal fatigue sets in. So don't disassemble/reassemble any more than is necessary.
Randy Sloyer has a "test rig" he uses to apply pressure, temporarily holding together cases & PCB's for testing -- that sounds like a good idea. I've tested quickly just pinching things together with thumb & forefinger, but that's got a lot of drawbacks, and may lead to false negatives.
If you care to sell the case, I've a working PCB that would LOVE to find a real home . . .