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The display of the Pocketronic consists of a strip of paper that slides from right to left behind a slightly magnifying screen. The stepwise movement is created by a solenoid, visible in some of the photos below. The solenoid is driven by the electronic circuit on the pertinax PCB, which covers the PCB with the three TI calculator chips. The small epoxy PCB on the other side of the machine contains the driver for the small thermal printer.

The power supply consists of two battery packs: one with six AA cells and one with seven 2/3-AA cells. They supply the two voltages used by the calculator (see second photo). The original charger is missing, so a temporary solution involves a simple connector, a dual power supply, and two resistors which limit the charging current to less than 10% of each pack's capacity. This allows for long-term charging without damaging the cells.

Charging seemed to go well; however, the batteries don't hold a charge for more than a few days (*). Once charged, the machine showed some life but didn’t calculate. Paper was wound around the rubber transport wheel, blocking further movement. After removing the sticky paper, the calculator worked fine.

However after some usage the paper transport blocked again. There appeared to be some decayed foam near the rubber transport wheel which got between the wheel and the paper. (See photo)

The initial print was readable but a bit faint. It is known that thermal paper ages. A piece of recently bought paper, cut to a width of 6 mm and glued to the original paper, showed a significant improvement. The output is now crisp and clear.

(*) The batteries are replaced by NiMH batteries, AA with a capacity of  1300mAh and 2/3-AA  with a capacity of 750mAh. All with a low self-discharge rate.  The charging current is raised to about 120 mA  resp.  60mA. (See photo)

Temporary charging  connector

Decayed foam