Preventive Maintenance; Environmental Considerations; Visual Inspection; Cleaning - Siemens 353 User Manual

Maintenance

10.2 PREVENTIVE MAINTENANCE

The objective for establishing a preventive maintenance program is to provide maximum operating efficiency.
Every preventive maintenance operation should assist in realizing this objective. Unless a preventive measure
reduces a Station's down time, it is unnecessary.

10.2.1 Environmental Considerations

The controller has been designed to operate within specified environmental parameters (temperature and humidity).
These parameters are listed in Section 13 Model Designation and Specifications. Additional information
concerning environmental contaminants is covered in Section 7 Installation.

10.2.2 Visual Inspection

As part of a periodic maintenance program, the controller should be visually inspected. When viewing the station,
scan for abnormalities such as loose, broken or stressed ribbon cables. Look for damaged circuitry and heat stressed
parts. Check for excessive dirt or dust build-up which may impede air flow and inhibit proper heat dissipation.

10.2.3 Cleaning

Circuit boards are conformal coated for protection against contaminants and should not be cleaned unless
accumulated foreign material is causing a problem. If cleaning becomes necessary:
1. Protect the station's electronic components from electrostatic discharge. Fasten a conductive wrist
strap around your wrist and ground the strap to the station's case, the panel, or a static dissipative
work mat. See the next section for circuit board handling guidelines.
2. Loosen the Display Assembly's two faceplate screws. One screw is above the numeric display, the other
behind the flip-down door at the bottom of the faceplate. See Figure 10-1 as needed.
3. Pull the Assembly from the panel about 1.5" (38 mm).
4. Look behind the Assembly and locate the display cable, then open the connector locking levers on the
Assembly mounted connector to eject the cable-mounted connector.
5. Clean the bezel with a mild, nonabrasive liquid cleaner and a soft, lint-free cloth - do not use a paper towel. Set
the Display Assembly aside.
6. Pull the board(s) from the case by grasping a board by an exposed edge. Do not use the display cable to pull
the MPU Controller board from the case. Since the board edge connector mates with a connector at the back of
the case, a moderate pull will be needed to extract the board.
7. Remove debris from case and board(s) using a soft brush or low velocity deionized air.
8. Insert removed board(s) into the case and carefully guide the connector end of a board to mate with the
connector(s) at the back of the case. Only when the connectors are mated should additional force be applied to
seat the board.
9. Hold the Display Assembly close to the open case and mate the display cable with the connector on the Display
Assembly circuit board. The cable is keyed.
10. Align the Display Assembly with the case and finger tighten the two faceplate screws. To ensure water
tightness, use a torque screwdriver set to 6 inch-pounds to tighten the screws. Alternatively, use a screwdriver
to tighten the screws until a slight resistance is felt - then tighten an additional ½ turn. DO NOT
OVERTIGHTEN.
11. Remove the wrist strap.
10-2
UM353-1
April 2012