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Calculators: Handheld: Prinztronic 48G

(c) Emil Dudek 2011

(c) Emil Dudek 2011

Size (actual): 72.5mm x 125.0mm x 21.6mm (max)  (w,h,d)
Weight 94g excluding batteries

Power:

3.0V DC, 2 x AA size batteries  It accepts an adaptor (3V DC 150mA, centre positive) through a socket on the top side to the far right. Do not use an adaptor when batteries are inserted.
Case: Slim and slightly squeaky three-piece case made from smooth black and light grey plastic.  The upper black section is raised (to accommodate the batteries) and printed with white text for the brand and model number.  Below this is a sloping neutral plastic display filter with more printed white text for the numerals.  The display is a bright with good viewing angle.  A metallic panel sits in its own recess and serves as the keyboard surround with some black text for the on/off switch.  The small keys are short travel with a loud click.
Display: 8 digit blue VFD, with a ninth digit for negative, memory and error indication.
Features: Standard four functions with percentages, change sign, square root, pi, squares, parenthesis and four function memory.
Age: 1979
Manufacturer: Prinztronic, made in Singapore, serial number 056555 on a sticker on the inside of the battery compartment.
Comments:

 

Compact calculator that is nice to hold with its smoothed edges.  The logic is quite sound with good recover but let down by negative square roots.   The original case is soft brown patterned brown plastic with open top and half-moon cut-outs to the sides. The high component count is mostly due to the DC-DC voltage converter circuitry for the display.  Very similar to the  Soverin 438.

Components: 1 x cpu: Texas Instruments TMS1045NL MY 7940 (week 40 of 1979) 28 pin DIL, 0.6" width black plastic
1 x 9 digit VFD unit: single tube flat front Futaba 9ST-10
2 x transistors
6 x diodes
6 x capacitors
3 x resistors
1 x transformer coil (for DC-DC conversion)
Boards: The main board ( SPL0063A Rev 1 Singatronics) sits face down on top of the keyboard assembly and joined by 15 short stiff copper wires.   The keyboard assembly (AW145340 REV A) is fixed to the front with numerous screws.  Not made for repair.
Construction: Held together by internal lugs only be careful not to damage this calculator if trying to open it.  I found the best way was to lever the rear section away at the top and then progress down the sides.  The rear section will then come away.

Logic comments: (C) is used to once cancel the last number entered and a second time to clear the whole calculator, so it is really a (C/CE) key
There is automatic constant on all four functions
Input overflow is suppressed, inputting a ninth digit is ignored
Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full eight-digit negative numbers
Divide by zero shows zero and "C? in the far left (ninth) digit and is recoverable using (C)
Overflow shows the shifted result with "C" (or ?E? if negative) in the left most (ninth) digit and is recoverable using (C)
The change sign can be used in mid-number entry but not before
Memory store is indicated by an upper "n" in the far left (ninth) digit
The (MRC) key is used once to recall the memory and a second time to clear it
Overflow in memory is flagged as above and holds the shifted result
Negative square roots are allowed and result in a negative number
No bugs found