To access the optical unit of the BiliDx machine, you will need to open the machine.

First, take out the battery. The battery compartment is on the back of the BiliDx machine’s handle. To open it, undo the screw using a Phillips screwdriver and lift off the cover. Then carefully prise the battery out of its housing.

Next, take the casing apart. Undo the six screws at the back using a Phillips screwdriver and lift off the casing.

Release the optical unit by undoing the four screws that hold it in place. You will need to use a Phillips screwdriver for this.

Then carefully lift the optical unit out part of the way so you can access the wires.

There are four connectors that plug wires into sockets on the circuit board. Pull each of these out.

You can then fully remove the unit.

One of the common faults with the optical unit is damage to the catch that holds the test cassette in place. When you slide the cassette into the slot, you should hear a click to show it is correctly positioned and secured. Sometimes, cleaning the machine can lead to fluid entering the slot and damaging this mechanism. We can open the optical unit to examine it. You need to undo the screws on the casing. Try to keep the lighting low while doing this.

The internal components are light-sensitive, and strong lighting or direct sunlight can damage them.

Also, do not touch the LEDs as they are very sensitive to damage. There are seven screws to undo in total. You will need a Phillips screwdriver for this. You can then open the unit.

With the optical unit open, you may be able to identify what is causing the machine to fail. Check for corrosion on the circuit board. Also check whether the LEDs are milky or discolored. If this damage has already happened, you will need to replace this component.

If there are signs of water or fluid but no sign of permanent damage, you may wish to dry around every part using compressed air.

You can then test the machine again to see whether this has solved the issue.

If test cassettes have not been clicking into place, check the switch mechanism that holds these in position. If there is a build-up of dirt, carefully clean the mechanism and check whether it then works correctly. If there is corrosion or other damage, you will need to replace the optical unit.

To reassemble the BiliDx machine, place the optical unit back into the casing.

Put all the wires back carefully, making sure they aren’t strained or pinched. You can then place the screws back into the corners of the optical unit and tighten these with a Phillips screwdriver.

Then you can reassemble the casing. Make sure that the power switch is in its right position as you push the two parts back together.

Place the screws back into the casing and tighten them.

You can then turn the BiliDx machine on and check that it is working correctly.