The Museum of HP Calculators

HP Forum Archive 01

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Help! LED problem
Message #1 Posted by Gary on 18 June 1999, 4:50 p.m.

I have a 34C with an LED problem. Randomly, segments of the LED's (all tops, bottoms etc. evenly across the board) disappear and only reappear if I squeeze the calculator front and back together a little bit. Anyone know what's loose inside and what the fix is going to be? Thanks, Gary

Re: Help! LED problem
Message #2 Posted by DaveC on 19 June 1999, 1:29 p.m.,
in response to message #1 by Gary

Ha! One of HP's less succesful ventures. The chips inside the early versions of the machines are held in place by a heavy plastic molding, held to the keyboard and case with clips, its come loose and the chips are not making proper contact. You may have dropped the machine and broken the clips (they are under some tension and the plasticisers in the plastic are going fast). What to do? Does the machine rattle at all? It may be possible to glue the pegs back. (Others may have opinions I have never tried this). It may also be possible to solder the chips in place. Alternatively general dampness in the air has affected the contacts. What to do? Disassemble and scrub the PCB contacts with Isopropanol alcohol (and the chips too).

In either case please note where the chips go and which way otherwise you may have more problems!

Thanks, Dave- it's fixed!
Message #3 Posted by Gary Milcheck on 21 June 1999, 12:12 p.m.,
in response to message #2 by DaveC

Dav, Thanks for the help. You described the problem exactly. The three plastic tabs which hold the board to the case (all on one side) were broken. I reglued them (with a flexible plastic glue), scrubbed the PCB with alcohol and reassembled. The old HP works perfectly again, like new.


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