Early Electronic Calculator TEAL Riccar Calculator

Manufacturer:  TEAL Model:  Riccar OEM:  TEAL Year:  1971 Form:  Desktop Functions:  Basic four, Accumulate Number of Digits:  12 Display Type:  NIXIE Display: Matsushita CD78 Logic Technology:  DIS,SSI,MSI Memory Technology:  MSI-MOS Diodes:  ~ 250 Transistors:  15 Principal ICs:  JMOS (µPD100,..) IC Complement: NEC µPD10A (1), NEC µPD10C (3), NEC µPD13C (10), NEC µPD101C (4), NEC µPD102C (2), NEC µPD105C (2), NEC µPD112C (1), NEC µPD116C (1), NEC µPD128C (3), Mitsubishi M5811 (3), Mitsubishi M5812 (2), Mitsubishi M5825 (3), Mitsubishi M58207 (1) FD1001 (3) (39 total) Tech. Data Level:  3 Tech. Data Source:  RE Tech. Data Pages:  22 Tech. Data: Schematic (pdf)

A design from TEAL (Tokyo Electronic Application Laboratory), OEM'd for Riccar Sewing Machine Co. of Japan. Riccar doesn't seem to have given this calculator a model designation, this may have been the only foray by Riccar into calculators. From the design and implementation it appears to have very shortly preceded or be contemporary with the Royal Digital I, another OEM product from TEAL.

This model features zero-blanking, unusual in Nixie and pre-microprocessor calculators, implemented at the expense of an additional IC and assorted components.

The unit shown here is in the possession of Jef Ongena of Belgium. It had been in his family since new, but stopped working in 2020. Jef set out to repair it and found the power supply had failed. Repairing the power supply however, merely uncovered another problem. Repairing that uncovered a third problem, and so it went for six major faults, including four bad JMOS ICs. An over-voltage situation from the power-supply fault had likely taken out the ICs.

After considerable effort, communication across two continents and a 'remote' reverse-engineering via photographs, Jef successfully restored the unit to full function.

Replacements for two of the failed ICs were scavenged from orphan boards from an unrelated defunct calculator. This was fortunate as JMOS ICs are very difficult to obtain for repairs, but no such luck was forthcoming for the other two, which were of more complex functionality. In the alternative, substitutes were designed and constructed from 4000-series CMOS ICs. See the JMOS page for some commentary on this approach for repairing JMOS-based calculators, and the schematic for details.

Notes:

There are other OEM designs from TEAL which repurposed the same case and closely similar keyboard layouts. These designs are visually nearly identical to this Riccar model, however many of them use an LSI chipset, not the JMOS implementation of the Riccar design. See for example, the TEAL ABC850 at Calcuseum.

Internal view. This is after repairs with two substitutes for failed JMOS ICs installed.	Main logic board with registers and state machine. The bad µPD105 IC at UF3 has been removed at the time of this photo.	Display board, with timing and keyboard logic.
The unit in the course of repairs, with a prototype of one of the IC substitutes being tested in situ.	The boards assembled with the two IC substitutes installed.