DATAMATH

DATAMATH CALCULATOR MUSEUM

Texas Instruments TI-1800

Date of introduction:	1997	Display technology:	LCD
New price:		Display size:	10
Size:	5.8" x 4.3" x 0.95" 148 x 110 x 24 mm³
Weight:	4.0 ounces, 112 grams	Serial No:
Batteries:	1*LR54 (30µA)	Date of manufacture:	mth 05 year 1997
AC-Adapter:		Origin of manufacture:	China (N)
Precision:	10	Integrated circuits:
Memories:	1
Program steps:		Courtesy of:	Joerg Woerner

This TI-1800 is a very useful calculator for Tax calculations combining both a large and bright display and a valuable appearance. Compare to the more basic TI-1795+.

Dismantling this TI-1800 manufactured in May 1997 by Nam Tai Electronics in China reveals a clever design centered around an unknown single-chip calculator circuit mounted in Chip-on-Board (COB) technology on a small double-sided printed circuit board (PCB) and powered by four solar cells and a small LR54 (LR1130) backup battery. With calculators sporting COB technology you find always two requirements for the PCB to balance:

• Keyboard: Simple technology and big area
• Calculating electronics and display connection: expensive technology and small area

Engineers at Nam Tai Electronics developed a smart and very economical solution; A larger, single-sided PCB is used for the keyboard and connected with a short flat flexible cable (FFC) to the smaller and very complex double sided PCB for the calculator electronics. Please compare this design with a TI-1795+ manufactured in 1996 by Kinpo Electronics and still using a conventional flat-pack housing and just one PCB.

Inspecting the PCBs of this TI-1800 calculator brought our attention to a small mark reading TI-1800 PD308-3, We spotted a very similar PCB-Mark already with the TI-1795+ and started compiling a list of the PCB-Marks on calculators manufactured by OEMs for Texas Instruments.

If you have additions to the above article please email: joerg@datamath.org.