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Calculators: Handheld: KingsPoint Micro Algebra (aka 8413)
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| Size (approx): |
86mm
x 155mm x 30-32mm
(w,h,d) Weight 262g excluding batteries |
| Power: | 6.0V, 4 x AA size batteries. It accepts an adapter/charger (No. 616, centre positive) through a socket on the top side to the far right. Instructions on the rear state that when the Battery Low light is on recharge batteries for 15 hours and you may use the calculator whilst charging. The batteries are held in a removable cartridge but it doesn’t appear that this could be swapped for a battery pack; just insert four AA-sized rechargeable cells. It appears to be a needless expensive configuration. |
| Case: | Square edged calculator made from two-piece patterned black plastic case. The majority of the upper section is covered in thick brushed aluminium panels that wrap over the edges. The top panel is printed with blue text for the brand and AC adapter reminder information on the top edge. The neutral plastic display filter has printed white text for the digit numbers and three extra indicators. It is slight raised and very slight tilted. Another metal panel surrounds the keyboard but is painted black with reverse out text for the switches and model name. The keys are soft touch, short travel and slightly wobbly and the switches do not protrude much making them quite fiddly. A large label on the back give basic instructions and examples. |
| Display: | 8 digit blue VFD, with three additional red LEDs for overflow, low battery and negative indication. |
| Features: | 4 function calculator with percentages and automatic two-function memory. Switch fixed decimal point capability. Semi RPN logic. |
| Age: | 1973 |
| Manufacturer: | Kingspoint Corporation, made in Japan, serial number 083-2100 (with an overprinted red K in the middle). |
| Comments: | Very solidly built calculator with early display system. The logic is OK for such an early machine but the semi-RPN system and lack of recovery are typically archaic. |
| Components: | 1 x cpu; Texas TMS0126NC 7327 (week
27 of 1973), 28 pin DIL, 0.6" width black plastic 8 x 1 digit VFD tubes with three additional isolated red LEDs 10 x transistors 19 x diodes 1 x bridge rectifier: General Instruments 5W05 7325 7 x capacitors 27 x resistors 1 x variable resistor 3 x resistor arrays 1 x transformer |
| Boards: | The main cpu board (PC-P631) sits on top of the keyboard assembly (3701553and mounts on two metal brackets with screws. They are joined by a 24-way black plastic block connector, of which only 22 connections are used. The display assembly uses the metal board mounting bracket as the bracket to hold the display tubes. |
| Construction: | Remove the screw from the back and the second one from inside the battery compartment area. The back easily lifts off. |
| Logic comments: | The (CE) key will cancel the last entry whilst the (C) key will clear the calculator |
| Input overflow is suppressed: keying in a ninth digit is ignored | |
| An overflow shows the result with the Overflow LED alight and is not recoverable | |
| Divide by zero results in zero and the Overflow LED alight and is not recoverable | |
| There is switched constant on multiply and divide only | |
| Negative numbers are shown by the Negative LED alight thereby allowing full eight digit negative numbers. | |
| It operates semi Reverse Polish Notation which takes a little getting used to: to perform 3-4 key in (3)(+=)(4)(-=) to give"-1" | |
| The change sign function can be used during mid number entry | |
| Negative square root are not allowed and show the result which is unrecoverable | |
| Battery low status is indicated by another red LED alight - therefore draining the battery even quicker! | |
| No major bugs found |
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The image on the
left shows the extremely dense main cpu board. The whole assembly is
dominated by the individual VFD tubes and the metal mounting
bracket. Underneath the display is the main Texas IC and loads of
components. At the bottom you can see the black
block connector, the keyboard side being two pins longer.
Notice at the top the large transformer and heat-sinks on the transistors and the unusual use of a bridge rectifier rather than four diodes for the VFD driver circuit. Compare with the main board of the Kingspoint 8412. |
