On the front side of the board, install the blue pushbuttons on the number keys and the white pushbuttons on the rest of the keys. Flip the board over and while putting pressure to ensure all the buttons stay fully inserted, solder the whole keyboard.

On the back side of the board, install the 8 LED display current limiting 1K resistors on the spaces labeled R1 through R8, just below the display.

On the back side of the board, Install the keyboard 4.7K resistors on the spaces labeled KR1 through KR3.

Flip the board over to the front and solder the resistors.

Depending on the version of the board, the displays are placed too close together. To make them fit, sand down the b,c,d, and e sides of the displays. Consult the diagram below:

[a DS1 b] [c DS2 d] [e DS3 f]

Install them in the front, flip the board over and solder them.

Flip the board over to the back and insert the Arduino Nano. Ensure the usb connector faces the word USB printed on the PCB.

Flip the board over and solder all the pins. Be careful to not touch the displays or the keys with the hot iron while soldering the Arduino.

Download the Sinclair Scientific Calculator sketches and libraries from here:

https://github.com/arduinoenigma/ArduinoNanoSinclairScientificCalculator/tree/master/SinclairScientific1

Upload the sketch to the Arduino Nano.

This sketch has a display self test feature. By pressing 0 while the Arduino powers up, the display will show all the digits lighted up. If 8 is pressed while all the 8 are lit, a longer display self test will be shown. Pressing C at any time will take the calculator to its home screen.

Flip the PCB to the front and install the power switch. Flip the board to the back and solder it.

Flip the board to the back and solder a 4 AAA battery pack to the terminals labeled VIN + -. Be careful with the polarity. As a strain relief, put a drop of Loctite Go2 Gel or hot glue on the back of the board where the power cables are soldered.

The battery pack can be attached to the PCB with 2 sided sticky tape. Add Go2 Gel for increased strenght.

Install 4 M2 standoffs on the four holes provided on the PCB.