Created Date: January 09,2001

Created by: Russ

Hi,

What type of 205 CPU is it? A 230, 240 or 250? Is the blinking a constant or some type of pattern?

On a 250 series CPU, the RUN LED blinks fast when it is in the process of a firmware update. Maybe that is the problem with yours?

Just a guess,

Russ O 'Rourke

Created Date: January 14,2001

Created by: Mike McClanahan

The blinking run light also will occur after the CPU has been fried by a lightning hit coming in from another module. We learned the hard way after replacing 3 CPU module in the same PLC that one of the output modules in the rack had been fried (as evidenced by the blown off components) and everytime we inserted the new CPU and powered up it immediately started blinking the run light and we could never communicate with it. ADC was also unable to get them out of the progrramming mode. So use caution when replacing that CPU and make sure that you don't see anything else wrong and I recommend that you don't install a new CPU in a rack which developed a blinking run light (which would not go away when downloaded with new firmware) without removing all other modules first and then re-installing them one at a time, at least it will only cost you 1 new CPU.

Mike

Created Date: January 16,2001

Created by: scottlee

Also look for low-voltage to the PLC base. Had a marginal switch contact that was arcing and nearly ready to go out. CPU was blinking with the same symptoms as you describe. Apparently, CPU was resetting every second because of low voltage, and that was enough of a draw to drop the voltage, which would increase while the CPU reset , ad nauseum... no comms, just as you described. This situation was probably rare, but when you spend 2 hours pulling your hair and CPU's out, you try to prevent others from suffering as well.

Created Date: January 16,2001

Created by: scottlee

Also look for low-voltage to the PLC base. Had a marginal switch contact that was arcing and nearly ready to go out. CPU was blinking with the same symptoms as you describe. Apparently, CPU was resetting every second because of low voltage, and that was enough of a draw to drop the voltage, which would increase while the CPU reset , ad nauseum... no comms, just as you described. This situation was probably rare, but when you spend 2 hours pulling your hair and CPU's out, you try to prevent others from suffering as well.