Reviving A 1974 Sinclair Scientific Calculator

When a treasure of retrotechnology fails to work, the natural next step is to have a go at repairing it. [Adam Wilson] found himself in this position when he acquired a 1974 Sinclair Cambridge Scientific calculator, and his progress with the device makes for an interesting read.

First up is something of value to all old Sinclair enthusiasts, he’s found a solution to the original battery connectors being prone to failure. A couple of parts stocked by RS can be used as replacements, which should save quite a lot of Sinclairs with crusty connectors.

Saving the connectors should have fixed the calculator, but only served to reveal that it had an electronic fault. Some detective work traced this to the power supply, which is a small switching circuit. The 1974 chip and associated coil had both failed, which rather drew the project to a halt. A second repair-or-spares Cambridge Scientific was sourced, and by good luck it happened to have a working PCB. So [Adam] got a working calculator, and we hope he’ll succumb to the temptation to shoehorn in a PSU from 2022 to get the other one working.

Anyone curious about this slightly unusual calculator should take a look at our teardown of one.