As the 60's ended and headed into the 70's, one branch of popular design headed off into the tacky. With earth tones in glossy plastic and fake-woodgrain mac-tac, this has got to be the ugliest calculator ever produced.
Otherwise notable for early use of a 7-segment display, in the form of individual gas-discharge tubes. Note the half-height zero in the display.
Based on info from Rick Bensene, this would be another repackaged Casio calculator. The logic and keyboard appear to be that of the Casio 122 (see Onno's Casio 122) with the 7-segment display replacing the Nixies of the 122.
Interior. Note how the two sandwiched logic boards tilt up so they can be removed from the card edge connectors.
Also note the empty transistor location on the power supply board.
The transistor had failed and had been running rather hot so the replacement has been moved below the board with a new heatsink.
Board A (12H-31 A) top. This is the lower board in the sandwich.
Board A solder side.
Board B (12H-21 B) top. Upper board of the sandwich.
The small plug-in board at the top of photo is a replacement for a failed uPD10 IC.
It plugs into the IC socket around the middle of board B.
Board B solder side.
Board C (12H-12 C) from the front ..
.. and from the rear.
Individual 7-segment gas-discharge display tubes are not common.
They were made briefly near the end of the nixie era but were soon superseded by multi-digit displays such as the Panaplex series.
|1969 (Philco SC1772 ICs stamped with 6921 and 6945)|
|Some corrosion on screws and nuts. No display.|
|Cleaned extensively. Most screws and nuts replaced during reassembly.|
|Main pass transistor in 24V regulator (2SD91) faulty.|
|Replaced with 2N3055, heatsink added.|
|Original power connector replaced with IEC standard.|
|Broken Subtraction key reed switched replaced.|
|Accumulator function not working, GT key returns constant 666...665.|
|Solder pad at corner of board A connecting clock phase T to pin 3 of IC AY2 (accumulator memory) had been broken off.|
|IC B2C3 (µPD10C) has been removed for use in another calculator.|
|Substitute constructed and inserted.|
|Upper right segment of all digits stuck on.|
|To be traced.|
Calculators | Integrated Circuits | Displays | Simulations