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Calculators: Handheld: Commodore SR4148R
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Size (approx): |
80mm
x 150mm x 30mm(max) (w,h,d) |
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Power: |
6V sealed rechargeable batteries (3 x AA-sized cells). The adapter charger is used through a socket on the top side, in the middle. Use adapter DC640, 707, 708 or 709, 6 Volts, 400mA (centre positive). | ||
| Case: | Large, tilted and bowed case made from textured black plastic. The heavily inset, tilted and flat red plastic display filter gives a clean bright image though with a narrow angle of view. A recessed panel at the top holds a metallic sticker, printed black for the brand name. Bold coloured keys in red (two shades on my example), blue, grey and white are quite small, squishy, wobbly and make a soft click. | ||
| Display: | 10 digit red LED module with bubble lens (eleventh for minus sign) plus two digit (smaller) red LED module with bubble lens (third holds minus sign) for the exponent. | ||
| Features: | Standard four functions plus brackets, square root, squares, nth root, logs, powers, trigs, degree-radian, reciprocal, polar/rectangular coordinates, register exchange, stats, change sign, pi and two function double memory. Scientific notation 10 + 2. | ||
| Age: | 1975 - interesting to see that the main IC is 1974 | ||
| Manufacturer: | Commodore Business Machines, Inc., made in USA. Serial No. 082916. | ||
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Comments:
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With 48 keys is this a button monster or what! The SR prefix of this period indicates a "Slide Rule", they used "F" for financial. Good idea to install rechargeable batteries as this thing would have eaten power. This is one serious calculator, although the "Made in USA" means assembled at best as all the components and boards are Japanese. The cover is stippled soft black leatherette with top flap, fastened with a popper at the front. The logic is sound, if sometimes slow (three seconds for a Sin) but the lack of recovery and missing constant is a pain. |
| Components: | 1 x cpu: Commodore GHU-03A
7439 (week 39 of 1974), 40 pin DIL, 0.6" width 2 x IC: ITT 546A-5N 7529 (date code week 29 of 1975), 16 pin DIL, 0.3" width 1 x IC: Commodore GHU-01A ESR-T 7545 (week 45 of 1975), 16 pin DIL, 0.3" width 1 x 14 digit LED unit with bubble lens 1 x transistor 1 x diode 4 x resistors 2 x capacitors 1 x voltage control subassembly |
| Boards: | The main board sits lose on top of the keyboard assembly and is joined by a 21-way ribbon cable. |
| Construction: | Remove the two long screws at the rear. The back section lifts off easily, hinging from the bottom. |
| Logic comments: | The (C) button is used to clear last entry of a number and pressed a second time to clear the whole calculator. |
| Overflow on number input is suppressed, typing in an eleven digit number ignores the eleventh digit. | |
| An overflow error is flagged with an "E" in the eleventh (left most) digit, negative or positive. Number is not recoverable. | |
| Divide by zero results in a "E" which is also not recoverable. | |
| There is no constant on any function | |
| There is no indication of memory store - you have to remember it. | |
| Calculations appear to be to 12 digits. Try this; "1.000000001" then (square root), which display "1", now (-)(1) gives 4.9 x EE-10 | |
| Negative numbers are flagged by a "-" sign in the eleventh left digit | |
| The change sign function can be used in mid number entry |
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Once open you can see the complex fit inside. Everything is orientated to getting the rechargeable batteries in the top area. In my sample a long since perished rubber band is designed to hold these batteries to the rear section of the case - held by two lugs. Most of the components (including the main IC) are hidden by the numerous ribbon cables. |
