Early
Electronic
Calculator
TEAL Royal Digital I Calculator

Manufacturer: TEAL
Model: Royal Digital I
OEM: TEAL
Year: 1971
Form: Desktop
Functions: Basic four
Number of Digits: 10
Display Type: VFI
Display:FUTABA DG12C
Logic Technology: DIS,SSI,MSI
Memory Technology: MSI-MOS
Diodes: ~ 300
Transistors: 6
Principal ICs: JMOS (µPD100,..)
IC Complement:NEC µPD10C (3), NEC µPD11A (1), NEC µPD13C (9), NEC µPD101C (2), NEC µPD102C (1), NEC µPD107C (1), Mitsubishi M5811 (2), Mitsubishi M5812 (3), Mitsubishi M58214 (1), Mitsubishi M58221 (1), Rohm TK2415 (1), Rohm TK2813 (4)
(29 total)
Tech. Data Level: 3
Tech. Data Source: RE
Tech. Data Pages: 16+17
Tech. Data:Schematic (pdf), Theory of Operation (pdf)

At a glance, based on it's size and vacuum-flourescent display tubes, this would appear to be an early LSI-based desktop from the early 1970s. The period would be correct - a 1971 date code was found inside. It's quite a bit smaller than the discrete and SSI-based calculators of the late-60s, so an LSI-based implementation would be expected, as by 1971 the transition to LSI was underway and a few LSI chipsets for calculators were available.

Opening it up led to a surprise though. It's built from the JMOS series of SSI/MSI ICs, along with lots of discrete components. Rather than being amongst the first of a class, this is one of the last, likely the last basic 4-operation calculator model based on this low level of integration. The designers managed to get the IC count down to just 29.

That's not a bad display tube in the right-most digit, it's an intentional half-height zero, produced by some special logic around the outputs of the 7-segment decoder.

Royal is actually Royal Typewriter Company, a then long-established typewriter manufacturer. This calculator model is fairly obviously of Japanese manufacture however. The calcuseum site shows the apparently same model badged as the Litton Feiler RC120, and indicating it was OEM'd by TEAL (Tokyo Electronic Application Laboratory).


Internal view.

Main logic board with registers and state machine.

Timing and display board.


- Unit Log -

Serial Number: 1G51400
Year of Manufacture: 1971 (PCB edge connector labeled 71.5.07)
Date of Receipt: 2020 Mar 27
Source: ebay Calgary
State upon Receipt: Good physical condition. Small piece cracked at rear of top half of case. '6' key is very bouncy.
Current State: Functional (2020 Mar).


Date: 2020 Mar
Symptoms: Bouncy '6' key.
Procedure: Bottom guidepiece of the keyswitch had fallen out, along with two small rubber bumpers that fit on the sliding tab. Bumpers set in place and guidepiece snapped back in. Guidepiece should be glued, may pop out again with too much force on key.


Date: 2020 Mar
Procedure: Broken piece of case top glued back in (CA). Also, crack found at right front of case, glued.



  TEAL Royal Digital I
Calculators | Integrated Circuits | Displays | Simulations
EEC
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