National Semiconductor NS107

Date of introduction:  1979 Display technology:  LCD
New price:  $39.95 (SRP 1979) Display size:  8
Size:  2.2" x 3.6" x 0.30"
 55 x 91 x 7 mm3
Weight:  1.4 ounces, 41 grams Serial No:  
Batteries:  2*LR43 Date of manufacture:  year 1980
AC-Adapter:   Origin of manufacture:  Taiwan
Precision:  8  Integrated circuits:  NEC uPD183xG
Memories:  2+1    
Program steps:   Courtesy of:  Ken H. Meine
    Download manual:   (US: 2.0 MByte)

National Semiconductor entered the market of Checkbook Calculators with the NS103 Data Checker in May 1978. 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 seven different family members:

1978: National Semiconductor NS103, 3 Memories
1979: This National Semiconductor NS107, 2+1 Memories, Credit card size
1980: National Semiconductor NS103A, 3 Memories
1981: This NSC Novus Electronics NS103A, 3 Memories
1981: NSC Novus Electronics NS101A, 1 Memory
1982: NSC Novus Electronics NS101A, 1 Memory, Gold
1982: NSC Novus Electronics NS100A, 1 Memory, Credit card size

Dismantling the featured NS107 manufactured around 1980 in Taiwan reveals a clean design centered around an unknown single-chip calculator circuit from the NEC uPD1833G family soldered on a double-sided printed circuit board (PCB) and powered by two small LR43 batteries.

Instead of the typical 3 Account Memories sports the NS107 two Account Memories with the associated [GT] Grand Total function and a completely independent, permanent Conversion Memory with three dedicated keys: [STO], [TO], and [FRM].

[STO] Store the displayed conversion factor in Memory 1
[TO] Multiply the displayed number and the stored factor
[FRM] Divide the displayed number by the stored factor

Inspecting the PCB of this National Semiconductor NS107 calculator brought our attention to a small mark reading 107, we spotted this PCB-Mark already on a Unisonic LC 262CK calculator sporting three Account Memories. We discovered on the PCB of the Radio Shack EC-306 Electronic Checkbook calculator a similar number and compiled a list of the PCB-Marks we discovered on similar Account Manager 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 6, 2020. No reprints without written permission.