![]() It's tempting to say get it replaced by HP while you can, but the replacement will probably be a 3V Chinese unit. It would be great if a fairly easy repair will fix it. Message #8 Posted by Ellis Easley on, 7:52 p.m., I have also seem a 12c keyboard with corrosion on the metal domes, but have not tried fixing such a problem. I resoldered the pin, and the keys are working ok, although self testing them fails sometimes. Then i pressed the corresponding chip pin, and presto - it started working reliably. I just checked continuity on the circuit board and checked keys - all ok. The cause was a bad solder on the single-chip - the pin was connected to all keys. ![]() It was on the entire row that contains 7,8,9 (and others) keys. I once got this type of problem on a Malaysian 12C. Message #7 Posted by Renato on, 5:30 p.m., If you used that method of repair on a 34C,it would be a grave error, also, it would not fix it. That method of repair is only meant to be used on certain flavors of LCD calculators. Would you care for the remains ? Maybe US trains work better. Maybe it was because it was in the box with all manuals, papers, case, charger, new batteries, etc. Message #5 Posted by Renato on, 1:06 p.m., (Brazil)įirst you go down to main street where the In response to message #3 by Vieira, Luiz C. Message #4 Posted by Norm on, 2:09 a.m., In response to message #2 by Randy Sloyer Here is Dave's picture of the strips in a 15C keyboard, the same as your 12C: You might see intermittent behavior when pressing the R/S key, as the common connection is near that key and the force of the key actuation could help make the common connection. If the strip looses contact with the keyboard scanner through the one connection point, the whole row of five will be dead. The keyboard is made up of eight strips of five keys each. The row of five keys R/S thru CLX should have the same problem. The Chinese units would be more likely to have this defect, but it certainly is possible in a 1999 unit. Nor will taking the batteries out for 24 hours as HP support recommends to "bleed off static charge". The battery gymnastics will not solve your problem. Message #2 Posted by Randy Sloyer on, 9:25 a.m., Should I try anything else before returning the unit? Any thoughts are appreciated. The unit is still under warranty for another couple of months. My understanding is that the step of shorting a wire across the batteries is meant for the case where the unit will not respond to any key input. The keyboard self test works until I get to those keys, then gives “Error 9” when I get to XY, which indicates that the keys in question are not “talking” to the CPU. I have tried removing the batteries for about 15 minutes and it didn’t help. If I press the key many times, I can usually get it to work. The R/S and SST keys (and sometimes the R down key) don’t work intermittently (these are all in a row – keys 31, 32 and 33 per the program numbering). I have a Malaysian built HP 12C (1999 model if I am decoding the serial number correctly). Message #1 Posted by Stan (Sg) on, 7:26 a.m. HP 12C Keys don't work The Museum of HP Calculators
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