15C Keyboard Test Error


If a 15C has an "error 9," it has failed the keyboard test. But what does that mean?? All they keys seem to work, it just fails the test. Could a low battery cause this problem? I am asking for a friend who says it has a low battery indicator, but he doesn't have new batteries to test it.

Edited: 26 July 2003, 3:13 p.m.


All bets are off with a low battery indicator. Get new batteries and try again.

Error 9 means a key did not register or was pressed out of sequence during the test.


If all the keys seem to work Ok, there are two reasons why you may get Error 9, one being if batteries are indeed *very* low, and the other being that you (or your friend) aren't pressing the keys in the correct order.

You must press them from left to right, one at a time, beginning with the topmost row, and must press the vertical ENTER key *twice*, once for each row it spans, i.e: you must press them like this:

   - press "Square root"
- press "e^x"
- ...
- press "divide"
- press "SST"
- press "GTO"
- ...
- press "X"
- press "R/S"
- ...
- press "arrow left"
- press "ENTER"
- press "1"
- ...
- press "-"
- press "ON"
- ...
- press "RCL"
- press "ENTER"
- press "0"
- ...
- press "+"
If all goes well, you should then get a "15" right in the middle of the display. Else, either you did press one key out of sequence, or then the last key before you get an "Error 9" is malfunctioning.

Please try above sequence and see if this time it passes the test Ok.

Best regards from V.


The owner's manual describes Error 9 as follows:

Error 9: Service
Self-test discovered circuitry problems, or wrong key pressed during key test. Refer to appendix F.

Appendix F relates to "Battery, Warranty, and Service Information."

Problem could be batteries?



Hi, professor;

in digital circuits, voltage levels below a minimum recommendation may cause the most strange and weird behavior, believe me. We're talking about MOS-based digital circuits, and in this case we may have larger voltage ranges, but if you consider that pressing a key in these calculators increases current consumption in about 300%, then having a previous low battery condition may lead to malfunction when a key is pressed, even if it is not when keyboard test is performed.

I observed once that ealier HP15C's with batteries "nearly-to-low-bat-condition" will sign this low-bat condition (flashing *) when performing keyboard test even when no keys are pressed, but will behave oppositely when in normal operation. I think these tests ([ON]&[+], [ON]&[×] and [ON]&[÷]) are like running programs and consume more power than regular use. If this is true, low batteries may cause [Error 9] in a normal unit running keyboard test.

My 2¢.

Luiz (Brazil)

Edited: 26 July 2003, 11:12 p.m.


Are you sure you pressed twice the <ENTER> key ?


Thank you all for your inputs. I pulled out an 11C, and found some near dead batteries. It went part way through the KBD test, and got the error 9. With good batteries, it was fine. So I contacted my friend and found out that he got the 15C to pass the KBD test one time out of several. As previously mentioned, it had a low battery indicator - Looks like that's the problem.

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