HP Forum Archive 20

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HP 11C suddenly won't turn on Message #1 Posted by Antonio Petri (UK) on 20 Sept 2011, 6:36 a.m. I have an HP 11C that I use very rarely. I was doing a simple calculation and the display suddenly started flashing; The calculator became unresponsive and I had to take the batteries out to turn it off. When I put back the batteries the only thing that the calculator did was to display the message "Pr Error", and it was still unresponsive at any key press, including the "on" key. I then removed the batteries again and waited a few minutes before to put them back, and the result is now that the calculator doesn't even display the "Pr Error" message and it doesn't turn on at all. The batteries are ok as I have tested them on my 15C. I wonder whether what this problem is and most importantly, whether I can get my 11C working again. Antonio

Re: HP 11C suddenly won't turn on Message #2 Posted by uhmgawa on 20 Sept 2011, 8:57 a.m., in response to message #1 by Antonio Petri (UK) Quote: I have an HP 11C that I use very rarely. I was doing a simple calculation and the display suddenly started flashing; The calculator became unresponsive and I had to take the batteries out to turn it off. When I put back the batteries the only thing that the calculator did was to display the message "Pr Error", and it was still unresponsive at any key press, including the "on" key. I then removed the batteries again and waited a few minutes before to put them back, and the result is now that the calculator doesn't even display the "Pr Error" message and it doesn't turn on at all. The batteries are ok as I have tested them on my 15C. I wonder whether what this problem is and most importantly, whether I can get my 11C working again. Does the "Pr Error" still persist on the display when the 11c appears otherwise unresponsive? It may be the LC oscillator failing to start up coming out of power off. If you have access to an oscilloscope you can check for activity of the LC tank when the ON key is depressed. I've seen the r2d2 lock up on occasion and give the external appearance the unit as a whole is defunct. The dropout voltage for the cmos process used in voyager silicon is phenomenally low (a good thing). Removing the batteries for even a few minutes I've often found insufficient to cold reset the device. Shorting the battery terminals however will discharge the bypass capacitor and do the job. Other than this there isn't too much which can commonly go wrong with a voyager to make it appear defunct. Grab a 5-10x jeweler's loupe and have a look at the SMD solder joints on the lqfp packages. It is possible an intermittent connection has developed. In that event pressing down on any suspect lqfp leads with a wooden toothpick while trying to bring the 11c back to life would be my suggestion.

Re: HP 11C suddenly won't turn on Message #3 Posted by Antonio Petri (UK) on 20 Sept 2011, 3:30 p.m., in response to message #2 by uhmgawa Thank you for your detailed diagnosis. It happens that after about 8 hours since I removed the batteries the calculator is working ok again, I haven't done anything but putting the batteries back in. Yes, the "Pr Error" message stayed even when the calculator wouldn't respond to any key press; it disappeared when I removed the batteries for the first time. After putting back the batteries after about 15 minutes the calculator didn't turn on at all. So, I understand that, if it happens again, I will have to short the batteries' contacts, as you suggest, or... wait 8 hours again! Thank you again, Antonio

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