Posted 10 Jun 2017 during production, complete system was 'OFF' and found error LED was blinking in Q4A CPU. then checked and found CPU program was erased. why it was happened and what are the reasons... Share this post Link to post Share on other sites
Posted 10 Jun 2017 A couple of possible reasons 1. The CPU battery has expired. 2. Base issue 3. Transient spike on the power supply. When you reload your software, make sure you do a PLC Memory Clear first to make sure there is no redundant code left behind Last possible option is the CPU has failed, but this would be most most unusual for a Mitsubishi automation product. The last thought for me is, and this one is right out there, but I have had the issue is harmonics developed by variable speed drives. If the harmonic level in your power supply is high, usually the 5th harmonic, this can cause some very odd reactions with electronics in general. Just something to remember. Hope the above helps Colandra . Share this post Link to post Share on other sites