DATAMATH

DATAMATH CALCULATOR MUSEUM

Enterprex MC-2717 Checkbook Calculator

Date of introduction:	1983	Display technology:	LCD
New price:		Display size:	8
Size:	2.2" x 3.6" x 0.20" 55 x 91 x 5 mm³
Weight:	1.1 ounces, 32 grams	Serial No:
Batteries:	2*LR54	Date of manufacture:	mth 09 year 1984
AC-Adapter:		Origin of manufacture:	Taiwan
Precision:	8	Integrated circuits:	Sharp LI3329MT
Memories:	1
Program steps:		Courtesy of:	Ken H. Meine

National Semiconductor introduced already in 1978 with the NS103 Data Checker an electronic record keeper with three continuous memories to track bank and charge account balances with dedicated keys:

• Memory 1 [CHK] [DEP] [BAL] [A]
• Memory 2 [PMT] [CHG] [BAL] [B]
• Memory 3 [PMT] [CHG] [BAL] [C]
• Total sum of Memories [GT]

While the NS103 Data Checker was based on proprietary technology, introduced NEC of Japan with the uPD1833G in 1980 a single-chip calculator circuit that created the blueprint for checkbook-sized Account Manager calculators and thereupon the market got swamped with products based on this design. The uPD1833G simplified the use of the memories by removing the redundant [A], [B], and [C] keys and replaced the inconvenient three-way power-switch of the NS103 Data Checker with two dedicated [ON] and [OFF] keys and a [DS] key to toggle between two entry modes:

• Indicator (--) Floating decimal with manual insertion of the decimal using the [.] key
• Indicator (AM) Add mode with the decimal automatically put in the dollars and cents position (0.00)

Even the successor of the NS103, known as NS103A, switched its internals to the uPD1833G but we feature some more Account Manager calculators in the Datamath Calculator Museum based on this technology:

• Canon Checkbook - Missing the Toggle Key for the decimal mode
• Royal LCB 841 - The Art of Perfection in Japan
• Royal LCB 835 - Just one Memory (uPD1831G)
• Texas Instruments TI-2200 Checkwriter - Late, but not too late
• This Unisonic LC 262CK Check Master - Credit Card sized

NEC of Japan lost some market share with their design for Account Manager calculators in the Eighties, when competitors like Hitachi and Sharp introduced similar chips and finally lost the business completely to Toshiba's "Solar Cells" compatible design. Find more Account Manager calculators in the Datamath Calculator Museum:

• Canon Checkbook II - Toshiba inside
• Casio CB-80 - Hitachi inside
• Unisonic LC 224CK Check Master - Sharp Inside
• Texas Instruments TI-2200 II Checkwriter - Toshiba + Solar cells = Winning formula

Dismantling the featured MC-2717 manufactured in September 1984 in Taiwan reveals a clean design centered Sharp LI3329MT single-chip calculator circuit soldered on a double-sided printed circuit board (PCB) and powered by two small LR54 batteries. Learn how to decipher the 548A date code on the pictured Sharp chip.

Inspecting the PCB of the MC-2717 Checkbook Calculator brought our attention to two small jumpers to select between:

• (MR) Checkbook Calculator: [BAL/MR] doesn't clear the Memory
• (MRC) Standard Calculator: [MRC] does clear the Memory

This interesting feature allows the use of the same PCB design for both "Standard" and "Checkbook" calculators. Don't miss the Technico LC 741CK - a "Checkbook" calculator with [MRC] key.

The design of the Enterprex MC-2717 Checkbook Calculator was used with a NEC uPD1832G single-chip calculator circuit, too. Compare the APF Electronics 3552CK Checkbook Balancer. Obvious differences are:

• NEC uPD1832G [ON] and [CE/C] keys, display indicators left-hand side
• Sharp LI3329MT [ON/C] and [CE] keys, display indicators right-hand side

We noticed these differences with the Unisonic LC 224CK and LC 224CKE, too.

Learn more about single-chip calculator circuits used in Account Manager Calculators.

Don't miss the Corvus CheckMaster introduced by Mostek already in 1975. This rare product retains the balance of your memory even when shut off but uses power-hungry electronics.

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