DATAMATH CALCULATOR MUSEUM
Texas Instruments TI-1750 (2nd 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"
115 x 68 x 9 mm3
|Weight:||2.3 ounces, 65 grams||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|
|Program steps:||Courtesy of:||Stefan Klaes|
|Download manual:||(US: 0.8M Bytes)|
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:
|1st||mth 07 year 1977||213387||3*LR44||Toshiba T3532|
|2nd||mth 12 year 1977||119653||2*LR44||Toshiba T3603|
|3rd (early)||mth 10 year 1978||888828||2*LR44||Toshiba T3709|
|3rd (late)||mth 09 year 1979||711171||2*LR44||Toshiba T3709|
|4th||mth 10 year 1978||014178||2*LR44||Sharp LI3023M|
1st design use a very complex approach compared to other
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
• The 2nd 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)
• The 3rd 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 3rd design corrected this flaw and modified the battery holder
down for two cells.
• The 4th 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 1st 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 2nd design of the TI-1750 uses a battery holder to accommodate 3 coin batteries. One of them is blocked with a dummy battery.|
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.
all parts for a hint to possible manufacturers gives you the Sansyu
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© Joerg Woerner, December 14, 2002. No reprints without written permission.