HP Forum Archive 15

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HP15C - differences in displays Message #1 Posted by Artur - Brasil on 22 Oct 2005, 9:51 p.m. Hi to everyone! I was very surprised when I was trying to replace one 15C bad display for an HP12C display and they were not the same. The 15C has a higher serial number than 12C: 2901B17387 versus 2534B96550. Note the contacts in both displays and PCBs. The old ones are thin and compared to the newest model. Old HP-12C Newest HP-15C

Re: HP15C - differences in displays Message #2 Posted by Eric Smith on 22 Oct 2005, 10:08 p.m., in response to message #1 by Artur - Brasil Could you please post the part numbers of the chips in both calculators, as well as the part numbers of the circuit boards (typically 5180-xxxx, 00xxx-600xx, or 00xxx-800xx)? If it's not too much trouble, high-res photos of both sides of both boards would be nice. I'm collecting info for my Voyager internals web page, and would like to link each entry to example photos. I'm guessing that your 15C has the 1LQ9-0325 processor and uses a 4:1 multiplexed display instead of the older 2:1. The 4:1 mux only needs about 29 contacts (25 segments x 4 backplanes), vs. about 52 for 2:1 mux. The drawback of the higher mux ratio is that the contrast isn't quite as good. Unfortunately the displays aren't interchangeable, as I's sure you've realized. But it shouldn't be too hard to find a 12C of comparable vintage to the 15C, which should then have the 4:1 muxed display. Best regards, Eric Edited: 22 Oct 2005, 10:57 p.m.

Re: HP15C - differences in displays Message #3 Posted by Artur - Brasil on 25 Oct 2005, 8:30 a.m., in response to message #2 by Eric Smith Hi, Eric On the weekend I'll take the pictures, ok? Best regards Artur

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