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HP 15C: Difference between revisions
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== Construction == | |||
Earlier models of HP-15C are constructed using two board connected with a flexible piece. The screen board contains the LCD on the front, and initially three chips on the back, a combinational Display-Driver-RAM-ROM (1LE2-0321), containing 6x10 kilobytes of ROM and 43*56 bytes of RAM, another auxiliary RAM-ROM chip (1LH1-0302) and the CPU (1LF5-0302). The keyboard PCB is heat-staked into the top frame. Finally, a plastic ESD shielding tape and plastic sheet wraps around and shields the PCB. This model may be preferable as it is possible to swap out failed LCD with ones from much more available HP-12C. | |||
Later models switched to a single board design, with the entire PCB heat staked to the top frame. used a new CPU (1LM2-0001) with a Display-Driver-RAM-ROM (1LH1-0306), and finally an auxiliary RAM-ROM (1LH1-0302). | |||
Apparently the 1LM2 CPU is redesignated from the 1LF5<ref>http://www.brouhaha.com/~eric/hpcalc/voyager/variants.html</ref>. | |||
At some point this was changed to a two chip design, with the elimination of the auxiliary chip. This model is equipped with a Display-Driver-RAM-ROM chip (1LQ9-0325) and a newer CPU (1LH1-0302). With this change the LCD multiplexing is increased from 2:1 to 4:1 at a slight cost to contrast & worse ghosting. | |||
== Repair & Modification == | == Repair & Modification == | ||