Schematic
Texas Instruments TI-1025 Calculator: Reverse-Engineered Schematic
Schematic of the TI-1025 of 1979: TMC0923 chip, Itron FG85C1 tube, a 61.4 kHz charge pump to -22 V from a 9 V battery, and a 7 V 1.5 kHz square-wave filament supply.
Schematic
Schematic of the TI-1025 of 1979: TMC0923 chip, Itron FG85C1 tube, a 61.4 kHz charge pump to -22 V from a 9 V battery, and a 7 V 1.5 kHz square-wave filament supply.
(pins numbered left to right as viewed from top) 1 18 0V Sa Sa 8 DIGIT VACUUM FLOURESCENT 22 17 DISPLAY MODULE 9V Sb Sb itron FG85C1 +tip 21 16 a Sc Sc 33 20 f b 15 g 28 Sd Sd –9V 19 4 e c Se Se p 16 2 d Sf Sf 18 3 Sg Sg 27 17 VSeg IN 5 –22V Sp Sp 15 D8 D1 (relative to pin 1) 26 6 7 1 8 9 10 11 12 13 14 19 PUMP OUT pump, 61.4 KHz FIL 24 TMC0923 FIL 25 n.c.: 10, 23 ON 5 D8 1 4 7 OFF MC 14 C/CE 2 D7 each 13 4 key 0 2 5 8 +/– MR D6 4 12 3 D5 . 3 6 9 % M– 11 6 D4 9 2 = + – ÷ M+ D3 8 8 D2 7 1 3 5 7 10 9 D1 6 Notes • Digit scanning is LSD first. • Number cycle is approximately 190 Hz (5.2mS). • Filament supply is square wave of approximately 7V and 30% duty cycle, 1500Hz. • Capacitance in microfarads unless otherwise specified. • 2004 May 23: Initial drawing / bhilpert. 2020 Feb: Format updates / bh. Texas Instruments 1025 Calculator Page: 1 / 1 Printed: 2020 Feb 17