Prinztronic M

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Calculators: Handheld: Prinztronic M


		Size (approx):	54mm x 120mm x 16mm (max) (w x h x d) Weight 62g not including batteries.
		Power:	6.0V DC using 4 x AAA size batteries. It does not accept an adaptor.
		Case:	The brick-shaped compact case is made of three-piece smooth plastic design. The lower section is buff, the upper dark brown and the keyboard surround buff. A flat and flush red display filter gives a clear if limited angle of view image. The filter has the make and model number printed in white text. They keys are clear plastic with labels underneath. They are short travel, positive click and quite lose – the whole thing rattles like a box of matches.
		Display:	8 digit red LED with bubble lens with a ninth digit for negative and error indicators. Additionally there is a isolated red LED just below the eighth digit for memory indication.
		Features:	Standard four functions with percentages and four-function memory.
		Age:	1975 (the original receipt states 27 September 1975 when it cost £9.95 and 8% VAT (purchase tax)).
		Manufacturer:	No manufacturing details except made in Hong Kong. The serial number is 47561 on a sticker on the battery compartment cover. (I have also seen calculators for sale with serial numbers up to 656600).
		Comments:	Lovely to hold, these compact, Dixons sold calculators were a major break through in price at the time. The logic is poor with good recovery but let down by numerous bugs. The original cover is soft black plastic with external stitching, open top and half-moon cut-outs on the sides. It has an alligator skin embossed effect. This appears to be exactly the same as the Tabulex Gamma.

Components:	1 x cpu; (square G-type logo) C-595-1-15 7519 (week 19 of 1975), 28 pin DIL, 0.6" width 1 x IC: display diver; National Semiconductor NS510 DS/DM8864N, 22 pin DIL, 0.6" width 1 x 9 digit LED unit with bubble lens 1 x red LED; in line lead type 0 x transistor 0 x diodes 1 x capacitors 3 x resistors 0 x resistor arrays 1 x transformer; Astec AA2125
Boards:	The display board (026F) sits above the full length keyboard assembly/main cpu board and is held to it by two large pieces of tape.
Construction:	I do not recommend you try this one - it is very difficult. Gently push and twist a blunt stick on the right hand side looking from the rear. Inside the battery compartment you will just see a fixing lug. About 2cm from the top and the bottom there are others on this side. By the time these two are popped you can do the top and bottom lugs and finally the three on the other side.

Logic comments:	The (C) key is used to once cancel an entry whilst a second press clears the whole calculator
	Input overflow is suppressed as keying in a ninth digit is ignored
	Negative numbers are shown with a "-” to the immediate left of the number, travelling into the far left (ninth) digit, thereby allowing full eight digit negative numbers.
	There is automatic constant on all four functions
	Divide by zero just shows zero and “C” in the far left (ninth) digit and is recoverable using (C)
	Overflow shows the result and “C” (or “E” if negative) in the far left (ninth) digit and is recoverable using (C)
	There is indication of memory store by an individual red LED just below the digits.
	Overflow in memory is not indicated, but does happen and stores the shifted result - confusing!
	It suffers the divide to negative zero bug: (0)(-)(1)(=) to give "-1" then (/)(1)(0)(=)(=)(=)... etc will eventually give "-0"
	It suffers the pseudo fixed decimal bug: key in (1)(+)(0)(.)(0)(0)(0)(=) to give "1.000" which remains a three digit decimal number until more digits are needed or you use multiply/divide.