How to disassemble circuit board pen to replace refill

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Take apart pen on a table or surface that you wont lose any parts.
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Holding the pen body and the nib section, pull the circuit board section from the transmission assembly. It is a friction fit and may take some effort to pull it apart. Don't worry you wont damage anything pulling it apart.
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Once apart unscrew the transmission body by turning it counterclockwise. 
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Be careful to not lose spring once you pull the refill out. Replace with new refill and reassemble. Do not use pliers to tighten transmission, hand tight only.