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Calculators: Handheld: Monarch 800C
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Size (approx): |
78mm
x 138mm x 23mm
(w,h,d) Weight 136g excluding batteries |
| Power: | 6.0V DC, 4 x AA size batteries. Also accepts adapter (6V DC 100mA) through a socket on the top side to the far right. The battery compartment has a light blue ribbon pull to aid battery removal. The on/off switch is on the left hand side, half way up and has a blue printed metallic label. | ||
| Case: | Brick-shaped calculator made from two pieces of matt black plastic with rounded edges and a soft feel. A raised display area has a blue printed metallic sticker which sits in its own recess. Underneath is a flat, inset and tilted blue plastic display filter that gives a clean bright image. The keyboard area has yet another blue printed sticker that sits in its own raised recess. The keys are medium travel and a bit wobbly but work well enough. | ||
| Display: | 8 digit blue VFD with no extra digit | ||
| Features: | 4 standard functions only | ||
| Age: | 1975 | ||
| Manufacturer: | Monarch, made in Taiwan, ROC (Republic of China). My example has no serial number. | ||
| Comments: | Cheap and cheerful calculator that is actually quite pleasant as it carries the blue colour theme throughout: keys, display, stickers. Why they thought it needed two model stickers is a bit of a mystery - it looks as though there should have been an on/off switch on the front instead. The logic is OK with no major bugs but let down by lack of recovery and the strange handling of eight digit negative numbers. The original case is soft black plastic with a side and top zip and black plastic carry strap. |
| Components: | 1 x cpu: Texas Instruments
TMS0801NL P 7515-1 (date code week 15 of 1975), 28 pin DIL, 0.6"
width black plastic 1 x 8 digit VFD: single tube round face 1 x diode 3 x capacitors 17 x resistors 1 x transformer unit: DEE VAN DV 650 (this is a Taiwan power supply part) |
| Boards: | The main board is attached to the front with two screws and connected to the keyboard assembly via 17 wires. |
| Construction: | Remove (or at least undo them fully) the four screws accessible from the rear. The back section then lifts off easily. But be careful, the power cables are not that long and can be stressed when opening the case. Get the soldering iron ready just in case! |
| Logic comments: | The (CE) button is used to clear the last entry of a number and (C) to clear the whole calculator |
| Overflow on number input is suppressed; typing in a ninth digit is ignored | |
| An overflow error displays the result flashing and is not recoverable | |
| Divide by zero displays "0." flashing and is not recoverable. You can just see the number "90000" displaying just before the zero. | |
| There is automatic constant on all four functions | |
| Negative numbers are flagged by a minus sign in the immediate left hand digit but there is no ninth digit for it to travel in. However, you can almost use it: eight digit negative numbers are valid - you just cannot see the "-" sign! |
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Official winner of the "Strangest shaped
board" award for 1975!
The top right cut-out is for the adapter socket to sit but there appears to be no real reason for the curved bottom bits. The main Texas IC is obscured by the large, long-legged transformer unit - an unusual brand. |
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