Hello,

I have a PLC (CPU 1214C DC/DC/DC : 6ES7214-1AG40-0XB0) that was given to me by a customer. The customer stated that the PLC wasn't functioning properly and they replaced it with a new unit. Upon inspection, the processor seems to be working correctly. The input indicators illuminate when I apply 24VDC to the input and I also see the input transition to TRUE in the watch table. The output indicators illuminate as they should when using a test program I created BUT there is no power being passed to the terminals and one of the outputs (Q0.5) is constantly passing 24V although the logic state is FALSE.

I am using TIA Portal V14SP1 and I have updated the PLC to firmware v4.2.1.

I have opened the unit and looked at the components on the circuit boards but didn't see any obvious damage. Any thoughts on what else I can do/check? Any suggestions on what components may need to be replaced?

Thanks!

Hello,

you can try make Factory reset, hope all will be solved.

Thanks for the input. I forgot to mention, that was one of the first things I tried. Just to be sure, I tried it again just now and the results are the same.

I'm assuming maybe the output transistors have been damaged somehow...?

The signal ground or common power connection of the machine is very possibly the bandit that caused this. For this case a whole group of outputs can get damaged. There is a chance that the replacement PLC will also get damaged.

For individual damaged outputs can be of over current. What type of load was connected to the outputs?

I'm not certain what the outputs were driving - probably valve solenoids if I had to guess.

They were going to throw the PLC away and I asked if I could have it to see if I could fix it...that's where I'm at now. I may order new transistors and replace them.

I noticed that there are 3 circuit boards inside the unit. Does Siemens sell replacement boards? I assume I could probably buy a complete unit for what one board would cost, though...?

AiiRG

I'm not certain what the outputs were driving - probably valve solenoids if I had to guess.

They were going to throw the PLC away and I asked if I could have it to see if I could fix it...that's where I'm at now. I may order new transistors and replace them.

I noticed that there are 3 circuit boards inside the unit. Does Siemens sell replacement boards? I assume I could probably buy a complete unit for what one board would cost, though...?

Inductive loads are prone to fusing transistors if there is no protection circuit.

Even without outputs the PLC is useful to test run programs that rely on calculations or Ethernet communication testing. IO can be extended also.

Not sure if Siemens would sell the boards.. especially if they are not allowed to inspect the equipment first and charge you a heavy fee.

So I was looking at the circuit board again today and I noticed what appears to be a surface mount resistor that has been blown apart. If it indeed got hot and blew apart, I really don't see how it ended up in the current orientation but I suppose stranger things have happened.

Does anybody have a CPU 1214C DC/DC/Dc that they can compare this to or a schematic for the board? If so, what is the correct value for the resistor? FYI - the right half of the resistor is tied to the common for the output circuit (3M).

Thanks!