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Calculators: Desktop: Sharp Elsimate EL-2121

(c) Emil Dudek 2011

Size (approx): 137mm x 180mm x 15-42mm  (w,h,d)
Weight 266g excluding batteries


6V DC, 4 x AA size battery, 0.32W.  Also accepts adapter (EA-11E) through a socket on top side on the right (centre negative 4.5V worked fine).
Case: Square design which slightly slopes upward.  The display slopes out at about 45 degrees making it quite prominent and perfect for use on the desk.  The top section holds the batteries with a front battery cover. It is a two-piece smooth plastic case in off white.  A large tricolour brushed aluminium panel surrounds the keys and switches with reversed-out text for the make and model number.  The subtle keys in black, grey, blue and red are squishy, long travel buttons.  They work well to this day.  The green display filter gives a bright and high contrast display.  There is a pretty naff looking "Made in Japan" sticker on the lower front keyboard surround.
Display: 12 digit green VFD with an extra symbol cluster for error, memory and negative indicators.
Features: 4 function calculator with percentages, mark-up, change sign, square root and four function memory.  Switches for floating/fixed decimal points and rounding options (which is also on/off).
Age: 1985
Manufacturer: Sharp Corporation, made in Japan.  Serial number 62021506 on a rear sticker.


A quality feeling calculator that I'm tempted to use on my desk today.  Very sound logic except for the lack of input suppression.  Oddly enough it appears to be the same IC as the Casio S-1 but a lot of the functions are not included (like extended floating point, backspace) and it is 12 rather than 10 digit!  Rather cleverly, a cut-out inside the battery compartment reveals the Sharp name on the main board.

Components: 1 x cpu: Hitachi HD38401A  5A 45 (the batch 45 of January 1985?), 36 pin DIL, 0.6" width
1 x display: Single flat glass tube, twelve digit VFD with symbol cluster
1 x transistor
6 x diodes
10 x capacitors
3 x resistors
1 x transformer; Sumida 1674 E513
Boards: The main cpu board and keyboard assembly is all one, full-size board.  It is attached to the front with five large screws.
Construction: Remove the two screws from the base carefully pop the lugs on the two sides (about level with the sharp logo). Hinge the front of the calculator off from the bottom.  Not easy so be careful.

Logic comments: The (CE) button is used to clear last entry of a number and (C) to clear the whole calculator.
Overflow on number input is not suppressed, typing in a thirteen digit number results in an error state which can be partly recovered by using the (CE) key.
An overflow error results in the number and an "E" in the symbol cluster to the far right and is recoverable using (CE)
Divide by zero results in an  "E" as above and  is not recoverable.
There is constant on all multiply and divide only
Square roots of negative numbers are not allowed but show a negative result and an "E" which is recoverable using (CE)
Memory store is indicated by an "M" in the symbol cluster to the far right.
Negative numbers are indicated by a "-" in the symbol cluster to the far right thereby allowing full twelve digit negative numbers
There is a on/off rounding switch for round (5/4) and round down (V)
There is a decimal point switch for floating (F) and ,3,2,0 and (A) two-decimal financial input mode.  The latter is like a cash register as keying in (1)(2)(3) results in the number 1.23
The (MU) mark up key works like a delta percent key ; to add 10% tax to ?2.50 key in (2)(.)(5)(X)(1)(0)(delta-%) which gives "2.75"
The change sign key can be used in mid number entry
It suffers the divide to negative zero (once) bug: key in (1)(+/-)(/)(1)(0)(=)(=)(=) etc  to eventually give "0.-", one more division sets it to zero, exposing the hidden extra level of precision. 

The picture of the inside is taken with the base of the case removed.  Notice that the reverse of this board also serves as the keyboard assembly.

There are quite a few unused holes so this might have been a generic board used for a variety of models.  The fact that it does not use all the functions of the IC supports this.

Most of the components are devoted to generating the high voltage needed for the VFD - these can be seen around the top left of the board.