OHAUS CKW-55, Service Manual

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CHAPTER 3 INDICATOR TESTING
3.6.2 Relay Testing (Cont.)
NOTE
: When testing the Relay board containing dc type relays, an Ohmmeter providing a minimum of
5 Volts DC can be used to verify operation. When testing ac type Relays, a small circuit consisting of a
low voltage (24 V AC) isolation transformer and small lamp (24 Volts) are required.
1. Remove each fuse and check for continuity. Replace defective fuses. See parts list at the rear
of this manual. If a fuse is defective, there is also a possibility that the associated relay may
also be defective due to over currents.
2. Apply power to the indicator. Refer to the instruction manual and set the Indicator up to provide
a test of each relay.
3. For dc relay types, use an Ohmmeter providing a minimum of 5 Volts DC and check each relay
operation for open and closed contact operation. If a relay is defective, refer to section 4.6
and replace the Relay or the complete board.
4. For ac type relays, fabricate a small test circuit consisting of a small isolation transformer of
24 volts and a test lamp . Wire in series with each relay output. Check each relay for operation.
If a relay or relays are found to be defective, refer to section 4.6 and replace the Relay or the
complete board.
5. When testing is completed, remove power from the Indicator and replace the relay cover
previously removed.
6. Reassemble the Indicator.