Early
Electronic
Calculator		 Facit 1123 Calculator

Manufacturer: Facit
Model: 1123
Year: 1969
Form: Desktop
Functions: Basic four, constant
Number of Digits: 14
Display Type: NIX
Display:Hitachi CD81
Logic Technology: SSI
Memory Technology: MSI-BIP
Diodes: 36
Transistors: 45
Principal ICs: M5300 Series
IC Complement:Mitsubishi M5304 (2), Mitsubishi M5310 (13), Mitsubishi M5320 (19), Mitsubishi M5330 (17), Mitsubishi M5340 (51), Mitsubishi M5352 (7), Mitsubishi M5373 (13), Mitsubishi M5391 (14), Mitsubishi M5962 (3)
(139 total)
Tech. Data Level: 2.7
Tech. Data Source: RE
Tech. Data Pages: 15
Tech. Data:list

Anomalies:
  • Entering more numerals after pressing the decimal point than the decimal point position switch is set for will produce odd results.
  • Division by 0 will result in an infinite loop.
  • Multiplication or division where the first operand entered was negated will produce odd results.
  • Multiplication or division with an operand greater than 12 digits will produce incorrect results.

Notes:
  • A switch connected appropriately to the remote connector on the bottom of the machine permits the calculator to be manually single-stepped through the state cycles of an operation. See the CMU page for more explanation, and the schematic for details.
  • See the Facit 1123 simulation.
  • Read the tale of fixing the Facit 1123.

- Unit Log -

Serial Number: 302.500
Year of Manufacture: 1969 (transistors stamped with 9C, capacitors with 6850)
Date of Receipt: 1970s
Source: Unknown.
State upon Receipt: Flaky, can't add.

Date: Jul 1996
Symptoms: No display.
Analysis: Master clock signal enters IC112 but does not exit.
Solution: IC112 replaced with 7400, rotated to accomodate differing pinouts.

Date: Jul 1996
Procedure: Portions of Power Supply rewired.

Date: Jun 1997
Procedure: DISP line on board 2 open due to corrosion of copper, patched.

Date: Jun 1997
Symptoms: Multiplication and division are okay, but addition results in double the correct sum.
Analysis: OCC connection to IC380-11 (X Register) open due to incomplete insertion of jumper connecting the two sides of the board at pin 380-11 (manufacturing flaw).
Solution: Resoldered.

Date: Apr 2000
Symptoms: Multiplication and division produce erratic results.
Analysis: Power supply determined to be unstable over warmup time.
Solution: VCC rectifier diodes and zener replaced.

Date: 23 Jun 2003
Procedure: IC112 replaced again with M5340 removed from obscure service unit circuit board.

Date: 06 Nov 2004
Procedure: Controller/Monitor Unit constructed.

Date: 05 Oct 2005
Symptoms: Left on overnight. Display shows all digits with multiple numerals. No response to keypresses. 6 LSD Nixies dimmer than others.
Analysis: Digit timing not functioning properly. '8' bit of digit counter not toggling. Resistance on IC142-2 circuit lower than others. Low resistance traced to input IC162-13, which sinks 85mA when tested after removal. IC142 also failed.
Solution: IC162 (5320) replaced with 7420, IC142 (5373) replaced with 74107. In this circumstance the 74107 is more pin-compatible with the 5373 than is the 7473.

Date: 06 Oct 2005
Symptoms: nOD0 observed on scope to being influenced by the main clock (high level being pulled down near but not quite to low threshold at main clock frequency).
Analysis: Input IC229-3 shows non-linear impedance to pin 2. Upon removal pin 9 or 10 also measures faulty.
Solution: IC229 (5340) replaced with surplus 5340.


  Facit 1123
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