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Calculators: Handheld: Decimo Super Vatman SSII

Size (approx):

83mm (max) x 132mm x 30mm (max)  (w,h,d)
Weight 138g excluding batteries.

Power: 6.0V DC, 4 x AA size batteries, 0.3W.  Also accepts adaptor/charger (undefined though 3V centre positive worked OK) through a top side socket on the right.   The on/off switch is located on the top side in the middle.  It is a three position switch labelled ON/OFF/CH the latter for charging batteries.
Case: Chunky two piece plastic case.  The bottom section is beige, top is matt black.  Oversized green display filter has painted logo and gives a bright display.  The Decimo logo is printed metal inset panel.  Keyboard surround is brushed aluminium and has one printed key label.  Top is slightly tilted upwards, including the back, which causes the calculator to rock, especially with no batteries to weigh it down. 
Display: 8 digit green VFD display with a ninth used for minus and memory indicators
Features: Basic four function with percentages, square root, reciprocal, squares, change sign, register exchange, memory exchange, parenthesis and four function memory
Age: 1976
Manufacturer: Manufacturer: Decimo Electronic Handy Calculator.  Made in Japan.  Serial No. SS 012483
Comments: Classic calculator that has a quality feel in the hand.  The logic is let down by negative square roots and the pseudo fixed decimal bug but has a useful range of functions.  Imbalance on the desk is odd.   For those non-UK viewers, VAT stands for Value Added Tax - the purchase tax system in the UK.

Components: 1 x cpu: Rockwell A5501CB 7623 (date code week 23 of 1976) 42 pin staggered DIL
1 x 9 digit VFD round single tube display
2 x transistor
3 x diodes
5 x capacitors
1 x resistor arrays
4 x resistors
1 x transformer: DCT-04 Zebra
Boards: The keyboard assembly (GK197-4 Gico Japan A5501 K-1) sits on top of the main CPU board (D-VATb-590C) and is joined by a 13-way ribbon cable. The main board has space and graphics for additional components.
Construction: Use the top coin slot to start you off separating the two sides.  Gently squeeze in the lower part and move along the calculator.  Warning - very difficult, if in doubt don't do it.

Logic comments: The Clear Entry key (C/CE) is used to clear an input number and pressed a second time to clear the calculator.
Overflow on the input of a number is suppressed typing in a ninth digit is ignored
There is automatic constant on all four functions
The negative sign is shown on the far left (ninth) digit thereby allowing full 8-digit negative numbers
An overflow is shown with the result and all decimal points alight and is recoverable using (C/CE)
A divide by zero or overflow error is shown by and is recoverable using (C/CE)
Negative square roots are allowed and result in a negative number
Memory store is indicated by the far left (ninth) digit decimal point
Overflow in memory flags the error and retains the original number
The (EX) key exchanges the operand and operator
The (MEX) key exchanges the contents of the screen (main register) with that of the memory
It suffers the pseudo fixed decimal bug: (1)(+)(.)(0)(0)(0)(=) gives "1.000" which remains a fixed three digit decimal unless more are needed or you use multiply or divide