HP Forum Archive 14

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HP-15C - are they all exactly same Message #1 Posted by Miki Mihajlovic on 26 Nov 2003, 9:35 p.m. Was there any difference among HP-15C during their production life. What I would like to know is there any difference between 1984 15C and 1988 15C. I know that the functionality and outside look is the same but what about the internal design, type of LCD, manual etc. My question boils down to: is there any advantage/disadvatnage in calcs produced one year over another.

Re: HP-15C - are they all exactly same Message #2 Posted by Raymond Del Tondo on 26 Nov 2003, 9:58 p.m., in response to message #1 by Miki Mihajlovic The greatest change I can recall was the chnage of the pcb, from separate pcbs for the keyboard & display to a single pcb for all components. While changing the pcb, they also changed the battery contact springs, or more precise, they reduced it to *one* single spring, and a static contact pole on the pcb side. As far a I remember from the units I opened so far, the also was a change in the pcb 'naming'. The old 11C pcbs hadd the 11 printed on, the newer 11C's used a 15C pcb, but with one memory chip less than the actual 15C. New pcbs won't fit into old style cases, mainly because of the changed battery contacts. There may be more differences, but I don't recall them now. Here are some people who know many more details about these nice machines, maybe they have better answers. Raymond

Re: HP-15C - are they all exactly same Message #3 Posted by Jim Chumbley on 27 Nov 2003, 8:50 a.m., in response to message #2 by Raymond Del Tondo "The old 11C pcbs had the 11 printed on, the newer 11C's used a 15C pcb, but with one memory chip less than the actual 15C." Does this observation shed any light on why the 11C does not have Register Store Arithmetic? (2 STO X 14) = 2 X Reg14 Stored Back Into Reg14. The 11C cannot do this, but the 15C can. I have long suspected this was just a bonding option at final PCB assembly, but I've never been able to see for myself. You could find such a bonding option if you find a bonding pad on, say, the CPU that has had a short bonding wire attached to it and run over to a grounded area.

Re: HP-15C - are they all exactly same Message #4 Posted by Valentin Albillo on 27 Nov 2003, 9:45 a.m., in response to message #3 by Jim Chumbley Hi, Jim: Jim posted: "Does this observation shed any light on why the 11C does not have Register Store Arithmetic? (2 STO X 14) = 2 X Reg14 Stored Back Into Reg14. The 11C cannot do this, but the 15C can." The HP-11C does have Register Store Arithmetic, but limited to registers 0-9. It doesn't have Register Recall Arithmetic at all, though. Best regards from V.

Re: HP-15C - are they all exactly same Message #5 Posted by Nelson M. Sicuro (Brazil) on 27 Nov 2003, 10:21 a.m., in response to message #3 by Jim Chumbley No, there is no such option in the PCB. The only difference is the ROM (inside the LCD controller chip) and an extra RAM chip in the HP-15C. In some time of the production, the PCB for the 11C and 15C (and 12C?) was exactly the same. Regards, Nelson

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