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Calculators: Desktop: Prinztronic C44

(c) Emil Dudek 2012

Size (approx):

150mm x 242mm x 72(max) mm (w,h,d)
Weight 1220g including cable and UK three-pin plug

Power:

Mains (240V 50/60Hz, 3.5W) powered only through a permanently fixed mains cable of considerable length.
Display: 8+1 digit green VFD the ninth digit (to the far right) is used for error and negative indication. 
Features: Standard four functions with switched constant. Semi-RPN logic. 
Age: 1973
Manufacturer: Prinztronic: Dixons International, made in Japan, serial No. D 4407433.
Comments:

 

A sturdy, large desktop from the early 70s which has very basic functions.  The logic is poor with lack of recovery, no trailing zero suppression on divisions and several bugs. I suspect this is made by Sharp.

Case and Design: A two-piece calculator made from smooth light blue base, textured dark blue upper section which produces a distorted wedge shape.  The front section has a metallic, black printed, label that sits in its own recess.  A green plastic display filter sits heavily inset at about 80 degrees and offers a easily read display.  The on/off toggle switch is located on the right and side near to top.

(c) Emil Dudek 2012

Keys and Switches: The keys in light blue off-white and red are long travel with a chunky hollow-sounding clunk on pressing and return.  The (+=) key sits a little more proud than the others. The on/off toggle switch is located on the right and side near to top. A constant slide switch has a metallic, black printed, label that sits in its own recess
Construction: Remove the four small screws from the rear, turn over and lift the front off, hinging at the bottom edge.  

Boards: The main board (PWBF1040CC-B) sits face up in the lower section. down.  It is held in place with two plastic lugs and the body of the screwed down mains transformer. It is connected to the keyboard assembly (QSW-K1061 QSW-K1034 3843524 3504283)  through a long 21-way ribbon cable  and three wires. The latter is attached to the front of the case with numerous screws.
Components: 1 x cpu: Hitachi HD3276P 3D (April 1973), 28 pin DIL, 0.6" width black plastic
2 x display drivers(?): Toshiba TM4356P 3-F (June 1973), 20 pin DIL, 0.3" width black plastic
2 x IC: Hitachi HD3253P 3F (June 1973), 16 pin DIL, 0.2" width black plastic
9 x 1 digit green VFD display individual tubes with eight segments (Futaba DG10Q1 31S)
1 x transistor (power 2SA473
1 x rectifier (SIRB-00)
4 x diodes
11 x capacitors
44 x resistors
2 x fuse (250mA AT)
1 x mains transformer (P1079CC)

Logic comments: (C) is used to clear the calculator and (CE) to clear entry function
My example does not have clear-on-power up function, which may be a defect
Input overflow is suppressed: keying a ninth digit is ignored
Negative numbers are shown with a minus in the (ninth) far right digit thereby allowing full eight digit negative numbers
The Constant function is switched in with the (K) switch and operates on multiple and divide only
The result of divisions do not have trailing zero suppression: (9)(/)(3)(+=) gives "3.0000000"
Divide by zero shows  "0.E" and is not recoverable
Overflow shows "0E" and is not recoverable
The logic is semi-Reverse Polish Notation RPN so to do 3-4 you input (3)(+=)(4)(-=)
It suffers the pseudo fixed decimal bug: (3)(+=)(2)(.)(0)(0)(0)(+=) gives "5.000" which remains a fixed digit number until division is used.
It suffers the divide to negative zero bug: (0)(+=)(1)(-) will give "-1", now repeatedly divide by ten to eventually give "-0.0000000"