DATAMATH

DATAMATH CALCULATOR MUSEUM

Texas Instruments TI-1750 (2^nd design)

Date of introduction:	December, 1977	Display technology:	LCD (yellow)
New price:	$19.35	Display size:	8
Size:	4.5" x 2.7" x 0.35"
Weight:	2.0 ounces	Serial No:	119653
Batteries:	2*LR44	Date of manufacture:	mth 12 year 1977
AC-Adapter:		Origin of manufacture:	Japan
Precision:	8	Integrated circuits:	Toshiba T3603
Memories:	1
Program steps:		Courtesy of:	Stefan Klaes
		Download manual:	(US: 555 kB)

With the TI-1750 Texas Instruments entered in 1977 the market of LCD-calculators. It is very obvious that it wasn’t manufactured by Texas Instruments. Even the internal construction looks different to typical Texas Instruments calculators like the later TI-1030. Which company is really behind the TI-1750 ? Comparing the TI-1750 with the Toshiba LC-844 gives the impression that is is a Toshiba design like their OEM calculator Radio Shack EC-264. Dismantling some TI-1750 from the Datamath Museum collection gives not only one but five different TI-1750 models:

Version	Date of manufacture	Serial No.	Battery	IC
1^st	mth 07 year 1977	213387	3*LR44	Toshiba T3532
2^nd	mth 12 year 1977	119653	2*LR44	Toshiba T3603
3^rd (early)	mth 10 year 1978	888828	2*LR44	Toshiba T3709
3^rd (late)	mth 09 year 1979	711171	2*LR44	Toshiba T3709
4^th	mth 10 year 1978	014178	2*LR44	Sharp LI3023M

	The 1^st design use a very complex approach compared to other LCD-calculators of that era like the Sharp EL-8020. A small detail is the connection between the LCD-contacts and the traces of the PCB. Instead the usual zebra-stripe (an arrangement of conductive and isolation rubber pieces) discrete coil springs are used.
	The 2^nd design still uses discrete coil springs to connect the LCD-contacts with the PCB traces but uses a smaller calculator chip in a 43-pin QFP (Quad Flat Pack) housing.
	The 3^rd design uses a much simpler approach and shows a huge cost reduction. It resembles the typical style of LCD-calculators sold in 1978. A funny detail is the battery holder accommodating two coin cells and one plastic dummy battery !
	Later models of the 2^nd design corrected this flaw and shrinks the battery holder down for two cells.
	The 4^th design looks nearly identical but uses different parts. The internal plastic frame of the housing and the printed circuit board were changed to use a Sharp calculator brain instead the Toshiba chips found in the other versions. From outside you notice the different position of the LC-display and the shape of the display frame.

The internal construction is totally different. The 1^st design uses a huge 42-pin DIL (Dual In Line) plastic housing instead this 43-pin QFP (Quad Flat Pack) housing.
The connection between the LCD and the PCB is done with small springs instead the later conductive rubber stripe.
The 2^nd design of the TI-1750 uses a battery holder to accomodate 3 coin batteries. One of them is blocked with a dummy battery.

There are different rumors which companies designed and manufactured the TI-1750, usually you get Toshiba and Sharp. Comparing the 4 versions with similar calculators manufactured by Sharp we could reject this speculation. On the other hand we can’t believe that Toshiba used a calculator chip from competitor Sharp.

Searching all parts for a hint to possible manufacturers gives you the Sansyu logo.

Sansyu Precision Co., Ltd. (Hieda, Japan) was founded in 1976 and specialized in precision plastic and metal processing. Main products are Injection Molding, Metal Stamping and Assembly. The construction of the TI-1750 makes heavily use of both injection molded plastic parts (display frame, internal frame, on-switch, keys) and sheet metal (housing top and bottom). Fits perfectly ! Let us assume that Toshiba designed the calculator and Sansyu Precision was responsible for both the tooling and manufacturing. It could be possible that the 1^st design was changed to both Toshiba and Sharp calculator chips to get a second source in the case of component shortage.

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