Commodore GL-976M GL-976MD

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Calculators: Handheld: Commodore GL-976M (aka GL-976MD) Custom Green Line

		Size (approx):	77mm (max) x 140mm x 30mm (max) (w,h,d) Weight 134g excluding batteries.
		Power:	3.0V DC, 2 x AA size batteries. Also accepts adapter (DC 420B) through a socket on the right side just above midway up.
		Case:	Three piece sturdy case in black and white matt plastic. The top front has an oversized green plastic display filter that is flush with the case an has a sloping inset section. It gives a bright image and it has the Commodore logo raised and painted silver along with the words "Custom Green Line". Bold red, white and blue keys have their own raised surrounds. They keys are wobbly and squishy but work well enough. Below the keyboard is a black printed metallic sticker with the company name, which sits in its own recess.
		Display:	7 digit green VFD with no eight digit
		Features:	Standard four functions with percentages and multi-key memory
		Age:	1975
		Manufacturer:	Commodore, made in Japan part no. 200556-02. Serial number 03445.
		Comments:	As you can see from the scan this calculator does possess a nine digit display - but the ones on the far left and far right are never used. Bold simple design that was to cover many calculators of the Custom Green Line series. The logic is good with good recovery and no detectable bugs in this rather basic but well designed calculator. The two key memory system is a bit arduous but you get used to it. Interesting that the main cpu board identifies itself as a GL-997R!

Components:	1 x cpu: Commodore GRBP-67 7536 (week 36 of 1975), 24 pin DIL, 0.6" width 1 x 9 digit VFD, single tube flat face 2 x transistor 6 x diodes 5 x capacitors 2 x resistors 2 x resistor arrays 1 x transformer
Boards:	The main cpu board (GL-997R PCB NO.200752 Rev A) sits on top of the keyboard assembly (SI 1676) and is held in place with the adapter socket. The two are joined by a long 14-way ribbon cable and the latter is fixed to the front with ten screws. The display power circuitry is situated on a mini board.
Construction:	Remove the two screws from the back and then it gets very very difficult to open as the internal lugs on the sides are very tight. Damage is sure to result so I recommend you do not try. There is a white side lug about half way between the bottom and the adapter socket. You need to push the white section in whilst prizing with a blunt wooden or plastic stick. A second on the side, and one on the top start you going around. The rear eventually lifts off. It is just as tricky to get back together again.

Logic comments:	The (C) key is used to clear last entry of a number press again to clear the whole calculator.
	Overflow on number input is suppressed, typing in an eight digit number ignores the eighth digit
	An overflow shows the result with an "E" in the left (seventh) digit, negative or positive) and is recoverable by repeated division of ten or multiples
	Divide by zero results in a "E000000" which is also recoverable by dividing by 1
	There is no constant on any function
	Memory usage is by two key presses, i.e. (=)(M) to store, (+)(M) or (-)(M) to accumulate or decrement. Clear is (0)(=)(M).
	There is no indication of memory - you have to remember it
	Negative numbers are flagged by a "-" sign in the immediate left digit. However, as there is no eighth digit to travel into you are limited to six digit negative numbers
	The percentage key just divides by 100 - so it can also be used to recover overflows.

	The box at 85mm by 160mm is quite a bit larger than the calculator. The three colour design wraps around the left hand side whilst the right hand side is white and the back is black. The top has a sticker stating the model number and serial number. Printed in Japan.		One colour 16pp fan fold manual in English only. 110mm high by 65mm wide. Covers a range of models and mentions the numbering system. Covers the770D, 774D, 776D, 776M, GL976MD and GL979D. Quote: "Congratulations on your purchase of your new Portable Electronic Calculator. You have selected one of the finest, precision-built figuring instruments." "A tiny, solid state chip of silicon, no bigger than this letter "M," contains the brainpower for your calculator. Engineers refer to this miracle of super miniature wizardry as, "Large Scale Integration," (LSI). It is your assurance of optimum reliability and increased durability."
	The scan on the left shows the main cpu board - more sparsely populated than a lot of the Green Line series. The two resistor arrays and an extra diode sit under the display out of site. Notice the small piggy-back board at the top left which hold the majority of the voltage doubling circuit for the VF display. Interesting that this board identifies itself as a GL-997R!