Hach DR300 Service Manual page 43

Step Description
9 Snap the LED retainer in the optical unit.
10 Assemble the optical unit with the mainboard. Carefully insert
the pins of LED and detector into the plugs and press the
optical unit against the mainboard. Make sure that the optical
unit overlaps the mainboard for 2 mm.
Use protective glasses and cut the pins of LED and detector
on the compartment side of the mainboard to a length of 1 mm
over the plugs.
Note: Make sure that the contact surfaces on the mainboard are not
11
touched.
Picture
Repairs
41