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HP Forum Archive 20

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HP 35 Keyboard Malfunction
Message #1 Posted by aj04062 on 7 Aug 2011, 7:10 p.m.

I just got an early 35 with the BUG and a raised dot on the 5. I was testing it out after getting it going and I noticed the whole row of keys starting with the 1/x key register as different keys. I disassembled and cleaned the keyboard but that did not cure.


I cleaned the keyboard to motherboard contact some but not thoroughly yet.


Edited: 8 Aug 2011, 6:45 a.m. after one or more responses were posted

Re: HP 35 Keyboard Malfunction
Message #2 Posted by John Robinson on 7 Aug 2011, 11:53 p.m.,
in response to message #1 by aj04062

I'd look for corrosion shorting two of the "row" lines, which could be on the keyboard circuit board or on the logic circuit board. Although if two lines were shorted, then you would expect odd behaviour from two rows of keys. Maybe there is somewhat of a short from the row line to another line causing the problem.

Have you tested for continuity from a keyboard row all the way through to the CPU chip ?

Cheers, John

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