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Triumph-Adler Model 80C (EC21)

The German Triumph company was founded already in 1896 as a daughter company of the UK Triumph Cycle Company and manufactured bicycles. In 1913 the company split and started to manufacture office equipment, e.g. typewriters. After a merger in 1958 with Adler, the Triumph-Adler company was the 5^th largest manufacturer of office products and was sold in 1969 to Litton Industries, headquartered in Beverly Hills, California. Early in the 1970s, Litton sold, depending on the region, electronic calculators under five different brands: Adler, Imperial, Monroe, Royal and Triumph.

We acquired this Triumph-Adler 80C (Version 1, EC21) calculator in 2025 on our quest to complete the Characterization of Single-Chip Calculator Circuits manufactured by NEC (Nippon Electric Company) Corporation of Japan.

Dismantling the featured Triumph-Adler 80C calculator manufactured in November 1974 by Omron in Japan reveals a very compact design based on a single-sided printed circuit board (PCB) for the main electronics, a single-sided PCB for the keyboard and powered by four disposable 1.5 Volts batteries or an external power adapter. The design language of this Triumph-Adler 80C with its sliding metal cover to access the batteries was clearly influenced by the Model 81C introduced already in 1972 and based on the Anita 811 calculator. The successor of the Triumph-Adler 80C could be found with the Royal Model 90K, manufactured by Omron, too but using a much simpler housing.

The Main-PCB is centered around a µPD275 single-chip calculator circuit manufactured by NEC and the few other remaining components on the PCB are mainly used to generate the different supply voltages for the µPD275 and Vacuum Fluorescent Display (VFD) and to bias the anodes and grids of the display with respect to its filament.

To gain some knowledge about the differences between the µPD275 located in this Triumph-Adler 80C, the µPD274 used with the Prinztronic Asset and the µPD276 used with the Elite Model 3002M, we decided here at the Datamath Calculator Museum to give the featured calculator a full "Teardown Treatment" and share our findings accordingly.

Calculating Unit: The µPD275 located in the featured calculator is a variation of the µPD274, one of the first "true" single-chip calculator circuits designed by NEC. It features an integrated clock oscillator and both its segment and digit output drivers are interfacing directly with low-voltage VFDs up to 30 Volts. Here at the Datamath Calculator Museum we don't qualify NEC's earlier µPD271 as a true single-chip calculator circuit, it is using with the µPD261 an external segment decoder and driver chip for the calculator display.

Display: The featured Triumph-Adler 80C calculator manufactured in December 1974 makes use of an 9-Digit low-voltage VFD manufactured by Futaba and known as Type 9-ST-12, soldered with its 19 pins directly to the Main-PCB.

Display Driver: The term "low-voltage" Vacuum Fluorescent Display might be misleading when used together with a calculator powered by four 1.5 Volt batteries. Common VFDs used with portable electronic calculators are usually operated around 30 Volts, significantly higher than the 10 to 15 Volts operating voltage of single-chip calculator circuits used in the 1970s. While the first generation of Texas Instruments TMS0100 single-chip calculator circuits lacked any display drivers and left the choice of display technology to their customers, focused the second generation products mainly on Light-Emitting Diode (LED) technology. In or around 1974, most Western calculator designs still relied on rather expensive LED technology but Japanese companies like Casio, Sanyo, Sharp and Toshiba started to leverage the lower manufacturing costs of VFDs, instead. Texas Instruments introduced in 1974 consequently with the TMS0850 their first product series focused on battery operated VFD calculators and modified the integrated segment and digit output drivers to withstand up to -35 Volts. NEC on the other hand entered the marked of single-chip calculator circuits in 1973/1974 and focused immediately on compatibility with VFDs. The µPD275 chips are manufactured in PMOS technology, meaning the output transistors are "high-side" switching and the most positive voltage of the chip is labeled V_SS for 0 Volt, all other voltages in the calculator are consequently negative with respect to V_SS. Multiplexed low-voltage VFDs need a voltage difference between its filament and the grids and anodes of the numbers of around 30 Volts to light up and to avoid "ghosting" while scanning, the deactivated grids and anodes should be slightly lower than the filament voltage. An elegant and very common solution is found with this Triumph-Adler 80C calculator, too. The grids and anodes of the VFD are "pulled-down" with 17 resistors (150k Ohm) to around -27 Volts, the filament is biased to around -25 Volts (Zener Diode) and the µPD275 switches the relevant grids and anodes to around 0 Volt to lit them up.

Clock: The Triumph-Adler 80C makes use of the internal clock oscillator of the µPD275 single-chip calculator circuit with two dedicated pins and four external components. The primary section of the internal clock oscillator, Pin 1 (CR1/R_EXT/C_EXT) requires a resistor R_EXT1 to V_GG and a capacitor C_EXT1 to V_SS. The secondary secondary section, Pin 28 (SR2/R_EXT/C_EXT) requires another resistor R_EXT2 to V_GG and another capacitor C_EXT2 to V_SS. We identified two resistor/capacitor combinations R_EXT1/C_EXT1 with nominal values of 150 kOhm and 100 pF, respectively and R_EXT2/C_EXT2 with nominal values of 300 kOhm and 100 pF for a typical frequency of 32 kHz.

Power Supply: The Triumph-Adler 80C calculator is powered with four disposable AAA-sized 1.5 Volt batteries or an external 6 Volt power adapter and uses a complex DC/DC converter to generate a total of four voltages:

We measured the operating current of the featured Triumph-Adler 80C calculator for two different cases:

Calculating the power consumption at 6 Volts for the Triumph-Adler 80C results in about 200 mW displaying a '0.' and about 230 mW with all segments but the minus sign illuminated. A very interesting result, a Canon LE-84 calculator with a LED display and using four disposable 1.5 Volt Alkaline batteries and a DC/DC converter for its TMS0801 chip clocks in at around 100 mW displaying a '0.' and 320 mW with all segments lit; showing both an advantage and disadvantage of LED-based calculators versus their VFD-based counterparts:

Keyboard: The keyboard assembly of the Triumph-Adler 80C with the Date code 49.11.13 was manufactured by GICO in November 1974 and uses a sliding power switch and 19 spring-supported plastic keys pushing small fingers on stamped sheet-metal pieces against contacts etched on a single-sided phenolic PCB.

The µPD275 single-chip calculator circuit uses not only its 9 digit driver outputs D1 to D9 to scan the keyboard, it even includes a 10^th output D10 to accommodate up to 20 keys in a 10*2 keyboard matrix. The [C] key is connected directly between common voltage V_SS and the CL input of the µPD275 while the sliding switch for the Constant function is isolated from the keys with a diode mounted in the Main-PCB. The layout of the keyboard assembly of the featured Triumph-Adler 80Ccalculator shows consequently an arrangement with 10 keyboard scan lines, 2 keyboard return lines, 2 connections for the [C] key, 1 connection for the extra diode and 2 connections for the power switch.

A closer inspection of the PCB traces of the keyboard assembly reveals that the [=] key and the [+] key are actually wired in parallel, an interesting choice for a calculator using "Adding Machine Logic". When Texas Instruments introduced in September 1971 with the TMS1802 the first single-chip calculator circuit, it did not even sport a [=] key. Its [+=] and [−=] keys clearly demonstrated that the chip was designed to replace adding machines used in offices and not slide rules. Consequently were these two keys used to accumulate numbers in a register and some calculator designs even labeled the Clear key with [CA] for Clear Accumulator. With Adding Machine Logic the [+=] and [−=] keys always complete operations, meaning the key sequence [2] [x] [3] [+=] [4] [x] [5] [+=] is resulting in 20 from the evaluation of 4 x 5, the previous calculation of 2 x 3 = 6 was cleared in the moment the [4] key was pressed.

Later members of the TMS0100 single-chip calculator family like the TMS0119 used with the TI-2500 Datamath calculator, introduced the concept of a separate [=] key to allow mixed calculations with combinations of addition, subtraction, multiplication and division in Chain Mode. The calculator will be cleared pressing a number key after the [=] key. The key sequence [2] [x] [3] + [4] [x] [5] [=] will be evaluated in the order of its entry and consequently resulting in 50 from the evaluation 2 x 3 = 6, 6 + 4 = 10 and 10 x 5 = 50.

Triumph-Adler obviously tried to please all users and colored the [+] and [-] keys of the Model 80C blue and red, respectively to indicate its Adding Machine Logic but added an additional black [=] key to ease multiplications and divisions.

Here at the Datamath Calculator Museum we use the DCM-50A Platform to Characterize and Reverse-engineer Single-chip Calculator Circuits. Many designs of electronic calculators do not use all features of their calculator brains and it would be difficult to unleash the full potential of the calculator chips in these cases. Additionally are electronic calculators "closed systems" with limited flexibility to measure signals, change voltages or clock frequencies, provide additional input keys or even change the display technology or specifications additional digits. Core idea of the DCM-50A is providing a generic platform to access all features of a single-chip calculator circuit and with the DCM-50A (PLAYGROUND) we increased the scope from Texas Instruments products to offerings from their competitors in the 1970s, namely AMI, Cal-Tex, Commodore/MOS Technology, Electronic Arrays, General Instrument, Hitachi, Litronix, Matsushita, Mitsubishi, Mostek, National Semiconductor, NEC, Omron, RFT, Rockwell, Sharp, Toshiba, and Western Digital.

Puzzled by the discovery of the "fake" [=] key used with the featured Triumph-Adler 80C (EC21), we compared the Calculator Logic Implementation of the µPD275 with the Calculator Logic Implementation of the original µPD274 chip reveals three major differences:

Please notice that the Triumph-Adler 80C (EC21) doesn't support the Item Counter feature of the µPD275 chip.

If you have additions to the above article please email: joerg@datamath.org.

© Joerg Woerner, June 1, 2025. No reprints without written permission.