Unisonic LC 224CKE Check Master

Date of introduction:  1982 Display technology:  LCD
New price:  $19.99 (SRP June 1982) Display size:  8
Size:  2.7" x 6.0" x 0.25"
 69 x 152 x 6 mm3
Weight:  2.0 ounces, 58 grams Serial No:  
Batteries:  2*LR54 Date of manufacture:  mth 01 year 1983
AC-Adapter:   Origin of manufacture:  Taiwan
Precision:  8  Integrated circuits:  NEC uPD1832G
Memories:  1    
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 1.4M Bytes)

Unisonic entered the market of Checkbook Calculators with the LC 262 in 1979. It features Account Manager functionality with three permanent (till you remove the batteries) Memories and started a very successful product line. We discovered as of now ten different family members:

1979: LC 262, 3 Memories, Credit Card size
1981: LC 262CK, 3 Memories, Credit Card size
1981: LC 263CK, 3 Memories
1981: LC 224CK, 1 Memory
1982: This LC 224CKE, 1 Memory, Pen
1983: LC 224CKM, 1 Memory, Pen
1983: LC 223CK, 1 Memory, Credit Card size
1985: LC 225CK, 1 Memory
1988: LC 226CK, 1 Memory, Taiwan
1990: LC 226CK, 1 Memory, Thailand

Dismantling the featured LC 224CKE manufactured in January 1983 in Taiwan reveals a clean design centered around a NEC uPD1832G single-chip calculator circuit soldered on a double-sided printed circuit board (PCB) and powered by two small LR54 batteries.

Don't miss the LC 224CK sporting a Sharp LI3329MT chip in an otherwise identical package. 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 APF Electronics 3552CK and Enterprex MC-2717, too.

Inspecting the PCB of this LC 224CKE manufactured in January 1983 brought our attention to a small mark reading 310-2, most likely a reference to Type 310 and Revision 2 of the design (schematics and layout).

Please find an overview of the PCB-Marks we discovered so far on Account Manager calculators.

In addition did we notice on the PCB of the LC 224CKE 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.

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 Woerner, February 13, 2020. No reprints without written permission.