![]() There are surprisingly few pins going to the LCD board, and I reflexively buzzed them out to make sure they were continuous. ![]() North of the Z80, we see a ribbon cable going to the LCD. They don’t seem to be integral to the keypad matrix, but they might be stitched into the pours in order to provide additional cooling or noise reduction. It’s a little weird how many vias are on this board. It feels pretty good despite this, and the membrane contacts are very clean. On the other side of the case, the keypad has one single, very big membrane keyboard. Another point in favour of “something got spilled in here.” Here’s our friend, a Z80! This is of course a very small surface-mount CMOS variety, a 44-pin Z84C0008 which is rated to run at 8MHz (it appears to run at 6MHz.) There isn’t anything else on the board that’s obviously damaged, although the surface-mount capacitors near the opening for the backup battery are very sticky to the touch. Everything else, including the power supply, is scattered around the edges of the keyboard and battery compartment. There’s SRAM and a flash ROM, and what appears to be a big custom glue chip and gate array that probably implements all of the actual system 1. Two small Philips screws come off to get the RF shield off.Īs you can see, there’s not really much going on inside this big tall case except for the keyboard. Once the back is removed, it revealed this surprisingly wrinkly-looking cardboard RF shield. Then I worked my case spudger around the edges, which popped three clips loose. Opening the case took a fairly long T6 Torx driver. However, nothing was legible and the display just kept getting progressively more screwed up. Removing the CR1616 backup battery – which still reported a solid 3.0V on the multimeter, good work Panasonic – and reinstalling it made little difference, except now I could tweak the screen brightness and enter characters. ![]() This is likely to just be a display fault. I soon found, however, that I could push 2nd + ON to turn the calculator off, which means that the CPU and ROM are alive, and the calculator is listening to its keyboard. The brightness controls didn’t work, so I guess it’s not going to be that simple. Will my efforts add up to a working calculator? There’s also the small matter of me wanting a desk calculator with which to do binary/hex conversions, so I picked up this broken one to attempt to nurse it back to health. It’s got a Z80, it runs a BASIC interpreter with machine-language program support, and lots of fun homemade games were built for it over the years. Computer calculator texas-instruments ti83-plus lcd repairĪlthough it may not be considered an “old” computer, a TI-83+ from the futuristic year of 1999 has a lot of appeal.
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