Remove the top cover and open the side doors or remove the side covers of the instrument.
Disconnect the environmental sensor plug and the background filter plug from the inlet tube.
Disconnect the inlet tube from the analysers.
Depending on your instrument there are
Instruments with a single charger holding bar: Unscrew the three nuts and remove the bar.
Instruments with separate rings: Remove the three screws from both charger holding rings.
Take the charger out.
You may disconnect some coaxial plugs from the charger if the cables are in the way. Note that the plugs and sockets have corresponding numbers.
Pull the needle out with pliers or tweezers.
Carefully scrub the needle with tweezers or a sharp knife.
Push the needle back in. Make sure the needle remains straight.
Put the charger back and reconnect the plugs.
If you have instrument with the charger holder ring then tighen the ring screws first very lightly and then stronger step by step so that the charger is pressed down evenly from all sides.
Follow the steps in reverse to put everything back together.