OMRON K-type PLC Maintenance Guide

ALARM light cycle time exceeds 100ms or battery low check program efficiency, replace battery

RUN/ERR/ALARM do not light up. CPU hardware failure. Replace CPU

7.2 Programmer Error Messages

Message meaning processing

NO END INST program does not have END (01) written at the end

CIRCUIT ERR Check if AND LD/OR LD is used correctly for instruction quantity mismatch in logical blocks

COIL DUPL is controlled by multiple instructions to check if OUT, KEEP, DIFU, etc. reuse the same address for the same output bit

IL-ILC ERR IL/ILC unpaired ensures that each IL has a corresponding ILC

JMP-JME ERR JMP/JME unpaired check jump number

The subroutine called by SBN UNDEFD does not exist to check the subroutine number of the SBS call

STEP OVER: If there are more than 16 steps, reduce the number of step segments

***PROG OVER program exceeds memory capacity, removes redundant instructions or uses larger memory units

***ADDR OVER Address Out of Range Check operand address

7.3 Special marker diagnosis

SR1808 (battery alarm): The battery voltage is low and needs to be replaced as soon as possible (model 3G2A9-BAT08).

SR1809 (cycle time exceeding 100ms): Optimize the program or extend the watchdog time.

SR1903 (ER flag): Arithmetic operand not BCD, BCD conversion out of range, instruction operand error, etc.

7.4 Common operational troubleshooting

Fault phenomenon inspection point handling

Is the output bit of the motor not rotating (no output at the output point) driven by the program; Output unit power supply; Fuse inspection ladder diagram; Check the power supply of the output unit

Input signal does not respond to input bit status monitoring; Input unit wiring; Check the external switch of the input public terminal; Check input unit model matching

Is the timer not working? Is the TIM execution condition ON? Is SV 0; Whether to adjust the program in the interlocking area; Check IL conditions

Does the counter count whether the CP pulse is valid; Is R always ON to check the CP edge; Check the reset logic

Analog input unit settings for abnormal analog values; Range of measurement; Wiring inspection DIP switch; Check the signal source

Communication failure (link unit) unit number setting; Cable; Station number verification system manual

Chapter 8: Maintenance and Preventive Measures

8.1 Regular inspection items

Environment: temperature, humidity, dust, corrosive gases

Electrical: Input voltage (100~240VAC or 24VDC), grounding resistance

Connection: Terminal screws are tightened, cables are undamaged, connectors are locked tightly

Battery: Replace every 1-2 years or immediately when SR1808 is turned on. Before replacing the battery, ensure that the PLC is powered on (otherwise the program may be lost), and then turn off the power before turning it back on.

Heat dissipation: Remove dust from ventilation holes

8.2 Program Backup

It is strongly recommended to save a copy of the program through a tape drive or EPROM writer after debugging is completed. The EPROM writer (C500-PRW06) can write programs to 2764 EPROM and then install them on the CPU for permanent storage.

8.3 Precautions for CPU Replacement

When replacing the CPU, it is necessary to read and write the DM and HR data (such as recipe and current counter values) of the original CPU into the new CPU through a programmer, otherwise it may cause abnormal operation. The entire program and data can be restored using a tape drive.

8.4 Safety precautions

It is strictly prohibited to disassemble units, terminals, or cables while they are powered on.

After power failure, wait for at least 1 minute (discharge of large capacitor), confirm that the POWER light is off, and then touch the interior.

Before conducting a voltage withstand test, the functional grounding terminal must be disconnected.

External hard wired safety measures such as emergency stop circuits and limit switches must be provided, and cannot rely solely on PLC programs.