Hi everybody,

I have a MPI network with the configuration above (see image attached). It work fine until the last week. The MPI bus started to go down, and we try to find the station or the cable that cause the problem. The problem was "solved" by disconnecting the station MPI 19 (S7-200 CPU). I change the CPU and the MPI connector and the problem remains.

What can I do more to test/diagnose the problem?

I change everything in that point and the situation is the same. Even if I remove for example, 2 stations from that MPI line and connect the station 19 the problem occurs.

Hello,

only for sure, not any new devices on bus in close history? Not any repair on bus before? What about terminators?

Duris_I

Hello,

only for sure, not any new devices on bus in close history? Not any repair on bus before? What about terminators?

Hi Duris_I

In close history there were no new devices. The last change in the BUS was near 2 months ago. And it was modified in the line of the MPI 10, MPI9, etc. The problem is when I connect the MPI 19 in the other line and it was OK until 5-6 days ago. The terminators are OK.

What is cable length of MPI bus cable?

IBN-Service

What is cable length of MPI bus cable?

 Hi,

Between stations and repeater-station  we are not exceeding 50m for sure.

Perhaps there is a problem with repeater?

Do you try to change both repeater - lines to see if error remain at same line?

IBN-Service

Perhaps there is a problem with repeater?

Do you try to change both repeater - lines to see if error remain at same line?

Hi.

Thank you for the tip. I try to change the lines in the repeater and things get a little better, because before the change, when we connect the station MPI 19, all MPI bus basically goes down and nothing works, after the change in the repeater, we can connect the MPI19 to the Bus without big problems, but a communication problem remains. When I connect the MPI 19 (I'm seeing the bus communication state with the Amprolyser), I see many frame errors and request repeats randomly only in the stations MPI 4, 14, 13,1,18, but the Bus remains "online". What I tried was connect only the PLC MPI19 with another power supply and it seems the problem is solved. I tested it during a hour and I only get 2 frame errors which it seems good. For some reason it seems that some interference in the 24VDC of that power supply is transported to the communication. We will check what is wrong with the main power supply of that electrical board.

You already replaced the MPI19 Station, including the plug...?

(It sounds a little bit that this station has a hardware - problem....)

IBN-Service

You already replaced the MPI19 Station, including the plug...?

(It sounds a little bit that this station has a hardware - problem....)

 Yes, as I said before, I already change the PLC and the plug and the problem continue. I connect the PLC with an external Power Supply and the problem disappear.