i have PLC fanuc 90 30. when i remove power from plc all program inside the PLC gone! and need to load program to PLC again!. the problem is POWER SUPPLY have a Battery to keep the program and LED of the battery is OFF. that's mean battery voltage OK. and strange is if i remove battery from P.S. the battery LED still OFF!! and in any condition (with battery or without battery) when i switch off the PLC all program gone!

 

check the battery voltage..probably a bad battery + a bad LED if the battery voltage is right then the backup power circuit is bad ..good luck

 

Maybe you have a bad power supply or bad rack, make sure there are no bent pins.

If this is an IC693CPU350 or above it has flash memory built in and that could be erasing the RAM on power up, check the configuration for this.

Also verify the battery voltage with a meter.

 

Check battery voltage alongwith a 1 Kohm resistor in parallel. Voltage should show above 2.5 V to be considered usable. Otherwise discard the battery. Battery backup will work till 2 V (Minimum voltage for CMOS SRAM chips).

Regards,

Tomy Zacharia