YSI 556 MPS - Manual (Page 98)

Section 11 Maintenance
YSI 556 MPS YSI Incorporated Page 92
Gold Cathode Cleaning
For correct sensor operation, the gold cathode must be textured properly. It
can become tarnished or plated with silver after extended use. The gold
cathode can be cleaned by using the adhesive backed sanding disc and tool
provided in the YSI 5238 Probe Reconditioning Kit.
Using the sanding paper provided in the YSI 5238 Probe Reconditioning
Kit, wet sand the gold with a twisting motion about 3 times or until all silver
deposits are removed and the gold appears to have a matte finish. Rinse the
cathode with clean water after sanding, followed by wiping thoroughly with
a wet paper towel. If the cathode remains tarnished, contact your dealer or
YSI Customer Service. Refer to Appendix E Customer Service.
NOTE: After cleaning, a new membrane cap must be installed. Refer to
Section 3.4.3 Membrane Cap Installation.
11.1.2 DO Sensor Replacement
1. Remove the probe sensor guard.
CAUTION: Thoroughly dry the sensor so that no water enters the probe
module sensor port when the sensor is removed.
2. Insert the long end of the hex key wrench into the small hole
in the side of the probe module bulkhead. Turn the wrench
counterclockwise and remove the screw. (You do not have to
remove the screw all the way to release the sensor.)
3. Pull the old DO sensor module straight out of the probe
module body.
NOTE: The DO sensor is not threaded, it is keyed, so it
cannot be removed by twisting.