Early
Electronic
Calculator		 Toshiba BC-1212 Calculator

Manufacturer: Toshiba
Model: BC-1212
Year: 1970
Form: Desktop
Functions: Basic four, accumulator, constant mode
Number of Digits: 12
Display Type: NIX
Display:NEC LD-955A
Logic Technology: DIS,SSI,MSI
Memory Technology: MSI-MOS
Diodes: 481
Transistors: 54
Principal ICs: JMOS (TM4000,..)
IC Complement:Toshiba TM4005 (7)
Toshiba TM4006 (3)
Toshiba TM4103 (15)
Toshiba TM4105 (1)
Toshiba TM4106 (2)
NEC µPD13 (10)
(38 total)
Tech. Data Level: 3
Tech. Data Source: RE & MF
Tech. Data Pages: 17
Tech. Data:list

Anomalies:
  • Division by 0 will result in an infinite loop.
  • Multiplication of a negative number will result in a very long or infinite loop.
  • Performing a division, followed by exchange and division by 1000 will expose the numerals of the first divisor which had been shifted into the hidden 4 digits of the registers.
  • Changing the decimal point position switch between entry of the operands during an addition will result in an incorrect sum.

Notes:

- Unit Log -

Serial Number: 165632z
Year of Manufacture: 1970 (sticker from Barr Business Machines (the retailer) on case says 1970)
Date of Receipt: 1970s
Source: Unknown.
State upon Receipt: Good physical condition.

Date: late 1970s
Procedure: Toroidal filter on line supply rebuilt.

Date: 30 May 1994
Symptoms: One digit staying on and bright, followed by complete failure of machine.
Analysis: Original 0.022 capacitors in digit drivers had inadequate voltage rating (180+24=204>200). Partial failure results in digit staying on and bright. Severe failure results in blown diode and 0-n IC.
Solution: Twelve digit driver capacitors replaced with higher voltage units. Blown diode replaced. Blown IC 0-? replaced with µP10 removed from Commodore DAC-612.

Date: Feb 2000
Procedure: Line ground connections redone.

Date: 15 Apr 2000
Analysis: 0.1µF filter capacitor on V+10 supply shorted.
Solution: Capacitor replaced.

Date: 15 Apr 2000
Symptoms: Arithmetic not working properly: 5+5 results in both 8 and 2 numerals on.
Analysis: Tens carry detector not detecting values in 10 to 15 range. Solder connection at pin 7 of IC 4-8 partially open.
Solution: Resoldered.


  Toshiba BC-1212
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EEC 		bhilpert