Teledyne 6712FR manual Opening the Controller Case, Replacing the Desiccant, To open the case

6712FR Refrigerated Sampler Section 8 Maintenance

8.6Opening the Controller Case

You will need to open the controller case to gain access to:

•The desiccant bag that dries the controller’s interior

•The battery that provides backup power to the controller

8.7Replacing the Desiccant

CAUTION

The circuit boards can be damaged from a discharge of static electricity. Always use an antistatic mat when opening the con- troller to protect the circuit boards.

To open the case:

1.Pull the discharge tube and pump tube away from the bulkhead fitting.

2.Remove the distributor arm by unscrewing the nut that attaches the arm to the distributor shaft. DO NOT

ROTATE THE DISTRIBUTOR ARM MANUALLY; THIS WILL SEVERELY DAMAGE THE DISTRIBU- TOR DRIVE GEARS.

3.Remove the controller from the refrigerator.

4.Open the case by removing the 11 screws that attach the case bottom to the case top.

Note

The case top and bottom fit together with a sealed tongue-and-groove joint. Any damage — nicks or cuts — to the tongue, groove, or sealing gasket prevent the case from seal- ing completely when you close it. Use extreme care when opening the case to avoid damaging the joining surfaces.

Refer to Figure 8-3for the location of the desiccant box. To gain access to the main circuit board and battery, remove the two dis- tributor connectors and the EMI shield.

A humidity indicator, labeled “INTERNAL CASE HUMIDITY,” is located to the right of the keypad. It indicates the amount of moisture present inside the control box. The paper indicator is blue when the control box is dry.

The control box is a completely sealed unit. You do not need to open the control box during normal operation. The 6712 Sam- plers use a desiccant bag inside the controller case to prevent moisture damage to its electronic components. Thus, the humidity indicator should remain blue under normal conditions. If moisture does accumulate, the numbered areas on the indi- cator will turn light pink or white, starting with the area num- bered “20.” This indicates that the relative humidity inside the control box exceeds 20%. As more moisture accumulates, the areas numbered “30” and “40” will turn light pink or white, indi- cating relative humidities of 30% and 40% respectively.

If the 30% area of the humidity indicator turns light pink or white, open the control unit, inspect it for leaks, and replace the desiccant bag.

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