HP Forum Archive 09

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HP 32SII Message #1 Posted by Howard Jones on 4 Sept 2002, 6:58 p.m. Could somebody please help me with my 32SII? Everything works fine but several keys (2, 5, 6 & 3) require much greater force to operate. Are there contacts that get gummed up or something like that? Help will be much appreciated.

Re: HP 32SII Message #2 Posted by Randy Sloyer on 4 Sept 2002, 8:06 p.m., in response to message #1 by Howard Jones Anything been spilled on the keyboard? If so, this would be the most likely culprit. The keyboard is scanned by the cpu in 6 columns across and 7 rows down. If it was a bad connection to the cpu board, a whole row or column would be acting up. What you describe, the loss of just 4 keys in 2 x 2 grid would seem to me to be something in or on the keyboard itself. It is a sandwich of 4 layers of mylar. Two of the layers are spacers with holes, one looks like a double sided pc board but it's made of mylar and the real guts of the keyboard is a single layer sheet that has 37 domes formed in it with conductive material inside the dome. When you press a key, you deform the dome with a snapping motion and the conductive dome bridges a pattern on the circuit underneath, completing the circuit. Any gunk on the dome or the circuit underneath will prevent the circuit from completing. The resistance is very high in these circuits, a minimum of 10k ohm for a completed keypress so it would not take a very thick spill layer to prevent a keyress from registering. Perhaps when you press hard, you are able to burrow past the spill and complete the circuit. A frequent contributor (Thanks David!) here reports good luck removing the batteries then giving the dirty keyboard three baths in an ultrasonic cleaner with fresh distilled water each time. Shake out as much water as you can, then dry in in an oven on low (< 150F) for several days.

Re: HP 32SII Message #3 Posted by Howard Jones on 5 Sept 2002, 5:29 p.m., in response to message #2 by Randy Sloyer Thank you Andy. When you say give the keyboard three baths in an ultrasound bath, do you mean I just take the batteries out and put the whole calculator in the ultrasound bath? Thank you.

Re: HP 32SII Message #4 Posted by Randy Sloyer(US) on 5 Sept 2002, 7:16 p.m., in response to message #3 by Howard Jones Yes, the whole unit gets the ultrasonic treatment as there is no simple way to take the case or keyboard apart. I would think 20 to 30 minutes for each cycle would be enough. Place it feet down in the tank as the newer 32sii's have printed keytops and you don't want to damage the legends by rubbing on the bottom of the tank. It is important to allow plenty of drying time (at least 2-3 days) after the final cleaning before re-powering. Do you know if anything has been spilled into to keyboard? It would be helpful to know, so that a best course of action could be planned.

Re: HP 32SII Message #5 Posted by Howard Jones on 5 Sept 2002, 11:14 p.m., in response to message #4 by Randy Sloyer(US) Randy, Sorry I don't know the history of this machine as I bought it second hand in a pawn shop for $Aust30. Thank you for your help. Howard.

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