Bad HP42S keyboard



I've bought a used, defective HP42S. It turns out that it works, sort of. It passes the automatic self-test, but fails with the keyboard manual self-test:

Sigma+ register STO, 
1/X registers RCL,
CLX registers TAN,
ENTER registers ENTER followed by RCL,
X<>Y registers Rdown,
+/- registers SIN,
etc etc etc.

All keys have a good pressing feeling; the machine has a lot of dirt underneath the keys. I'd like to know if the keyboard is easily fixable, if its worth opening the machine to fix it. I'd also like to know how to clean the keyboard bezel: i've tried once with a thin slice of a plastic rubber, but it creates a lot of dirt in the process..

Best regards



There is no easy solution for your 42S problem. The keyboard behavior your describe is most odd. I've repaired many a Pioneer and I've never encountered a similar problem. It is most likely some type of contamination on the logic board, shorting bus lines together. I have seen this phenomena on 48's due to no clean flux around the rom chip but never on a Pioneer.

It would be wise to remove the back and see what condition the internals are in. is the best place to start for opening instructions.

An ultrasonic cleaner is about the only solution for dirt inside the key switches. It is not practical to open the keyboard for repairs. It can be done but reclosing properly is not an easy task.

Edited: 8 Mar 2004, 8:09 p.m.


Thank you Randy

My fear is that the chip would be damaged... Do you know how often this happens with 42S units?

Thank You

Iuri Wickert


Chances are very small (<1%) that the cpu has been damaged.

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