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Calculators: Handheld: Sears Digi-matic D-8 (aka model 41024) Scientific Calculator
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Size (actual): |
78.5mm
x 159mm (approx) x 26.5mm (max) (w x h x d) |
| Power: | Integral rechargeable batteries (three 1.2V Ni-Cd x AA size batteries). It accepts an adaptor (undefined, but 4.5V centre positive worked fine) through a socket on the top side, to the far left. Operation time is quoted as six hours. | ||
| Case: | The case is two-piece black patterned plastic with a raised upper section (which helps accommodate the batteries). Most of the front is dominated by a brushed aluminium panel with black printed text for the key, switches and model name. The red display filter is thin, softly stippled plastic and is angled at about 20 degrees in a recess. It gives a clear and bright image with a good viewing angle. The squashy keys do have a positive click on bounce back. There is a large silver information / instruction panel on the back printed black. | ||
| Display: | 8 digit red LED (flat dot type) with a ninth digit for negative, function and error indicators. | ||
| Features: | Standard four functions, register exchange, powers, trigs, logs square root, pi, inverse, change sign, degree/radians switch | ||
| Age: | 1974 | ||
| Manufacturer: | Simpsons-Sears and Simpsons (Canada), made in Japan. Serial number 012046 | ||
| Comments: | Retail store branded calculator from Canada. If you search the web for this calculator you only get the Bowmar-shaped model. So I suspect that this was a later (and obviously very rare?) upgrade, or specific to the Canadian market as it has exactly the same name and model number. However, it does have the same case as the Digi-matic M8-2 four function calculator with memory, . The logic is not too bad and has a rare "deleted register" recovery function (which is not on the US model). The original case is padded and lined black plastic with three-sided zip and Digi-matic printed in silver on the front. |
| Components: | 1 x cpu: Rockwell A4001 15471PA
7434 (date code week 34 of 1974), 42 pin staggered DIL 0.6" width,
grey ceramic with metal cap 1 x IC: National Semiconductor NS413 DM8864M, 22 pin DIL 0.3" width black plastic (display driver) 1 x 9 digit LED module with red linear full length lens: ODA-9B 4 x transistors 6 x diodes 5 x capacitors 12 x resistors 1 x miniature variable resistor 1 x transformer |
| Boards: | The main cpu board (M20-D8, 0602441) is fixed upside-down to the keyboard assembly by 3 screws into plastic pillars. The keyboard unit (Jelco 49.10.15, Made in Japan, 6202401) (this is a date code of 15 November 1974) is assembled and fixed to the front with 10 screws. |
| Construction: | Remove the four screws from the rear and the back section comes off easily. |
| Logic comments: | The (C/CE) key is used to once cancel an entry whilst a second press clears the whole calculator |
| Input overflow is suppressed inputting an ninth digit is ignored | |
| Negative numbers are shown with a "-” in the ninth (far left) digit, thereby allowing full eight digit negative numbers | |
| There is an automatic constant on all four functions | |
| Divide by zero just shows zero and a small upper "n" in the far left (ninth) digit and is recoverable using (CE/C) | |
| Overflow shows the result and an upper “n” (“º” if negative) in the far left (ninth) digit and is recoverable using (CE/C) | |
| Negative square roots are not allowed and are not recoverable | |
| Extra functions are accessed by pressing the (F) key, and the decimal point of the far left (ninth) digits lights up to remind you | |
| There is no indication of memory store - you have to remember it | |
| The (X/Y) key is a register exchange whilst the (X/M) is a memory exchange | |
| The (DR) key recovers the last register even after the (CE/C) key is used - silly me, I was expecting this to be a "Display Restore" key as a power-saving function, but after waiting ages, I realised! | |
| It suffers the pseudo fixed decimal bug: key in (1)+(1)(.)(0)(0)(=) to get "2.00" which stays a fixed two digit decimal number until more are needed or you use multiply or divide |
