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6.4.2 Disconnecting RC Arc Suppression Circuits
Introduction
Relay contacts are protected by RC arc suppression circuits. Alternating current leakage through
these circuits may be sufficient to trigger very light ac loads such as neon bulbs, PLC logic
inputs, continuity testers, etc. If this leakage cannot be tolerated, the suppression circuits may be
disconnected as described below.
Procedure
Follow the procedure in Table 6-5 to disconnect the RC arc suppression circuits.
Table 6-5 Procedure for Disconnecting RC Arc Suppression Circuits
Step
1
Turn off the power to the Analyzer/Controller. More than one switch may be required
to remove power.
2
With the power off, open the case:
Grasp the bottom center portion of the front bezel and pull it downward and toward you
slightly to disengage the bottom of the bezel from the edge of the case.
Lift the bezel gently to disengage it from the top edge of the case.
Swing the bezel to the left. (The bezel and display assembly is mounted on pivot arms.)
The safety cover with its warning label will be visible.
3
With the power off remove the safety cover by removing the single screw holding it in
place.
Disconnect and tag all wiring from the terminal boards.
4
5
Remove the circuit card retainer clamp at the top of the case. Then slide all the circuit cards
half way out of the case.
6
On the right-most vertical printed circuit card (power supply) remove 330 ohm resistors R29
and R30 for Relay 1, and R31 and R32 for Relay 2 from the upper corner of the card.
If the auxiliary relays are installed, also remove 330 ohm resistors R39, R40, R44 and R45
7
from those optional assemblies (see Figure 6-1).
Reconnect all wiring removed in Step 4.
8
9
Replace the safety cover and secure it with the screw.
10
Close the case and power up the unit. Do not apply power until the case is closed.
7/99
9782 Series Conductivity/Resistivity Analyzer/Controller - Operator's Manual
Action
Input and Output Wiring
6-9
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