Dear Experts,

I have a problem with my Pc Adapter USB 6ES7 972-0CB20-0XA0, when i plug it in MPI or Profibus interface in S7-300 non of the LEDs are lit.

In manual they say it could be MPI cable not connected, which is connected as i downloaded one program from S7-300 last week, or hardware error, to inform customer support.

Did anyone had the same problem, and is it possible to solve it without customer support?

Thank you in advance!

Hello,

do you use the same cable like last week on the MPI or another one?
The same PLC?

The PLC is powered on? Which PLC you use ? Do the MPI interface support 24V Power on the Interface?

Regards

Christoph

Hello and thanks for replying.

I use the same equipment, on the same S7-300 PLC, tried to see something in online mode, but no LEDs, no connection.

The PLC has MPI and Profibus interface, I tried to go on Profibus, but no LED.

After this I tried to go online with friend's chinese PC USB adapter, it has all LED's lit, but when I try to go online, it causes CPU to go in Stop.

This morning I tried my original adapter on a different CPU, S7-300 314c, on a MPI interface, but still no LED.

The adapter needs a powersupply from the PLC. 
A standard mpi cable has only 2 wire (Pins 3 and 8). So the adapter will not work with it.
For the adapter you need a 4 wire cable, Pins 2,3,7 and 8.
As far as I remember the manual says, you have to use the short MPI/BP cable (about 30cm)  that came with the Adapter. (Because this is a 4 wire cable)

The FAQ https://support.industry.siemens.com/cs/ww/en/view/3001321 describes the interface on a S7-300/400 CPU

Dear Sir,

thanks for the answer, I understand what you are saying, but my problem is that the adapter worked on the same PLC last week, now it doesn't.

In the manual they say it could be hardware problem, is it possible to fix it without technical support?

Last I did was normal operation on the PLC, uploaded program from CPU, turned of Step7 and unplugged the cable, last week it worked fine, now nothing lights up, and I don't see it in Step7. 

Hello all,

I have the same situation. May be even more strange. I had a PLC which was working ok with the MPI adapter. Suddenly it stopped working as in the original post. I tried with both the ports and all the PGPC interfaces. But no LED is Lit. Now comes the strange part. PLC is communicating with SCADA over the same port. I checked with other PC adapter also but same result.

Any suggestions?

Kbv.

Hello,

i think the SCADA doesn't use the PC Adpater.

A normal CP for Scada need no power from the MPI Interface, only the Communication lines.

The PC Adapter need the Power and if on the PLC Port the Power Out is not working correct the PC Adapter is not working, but every other card which need no power can be work.

Regards

Christoph

Hello christoph,

The only possible explanation is that MPI and DP both ports of PLC are not giving supply out required for PC adapter to work. But how this can be possible and there is no error reported in PLC? Is there any way to resolve this?

Kbv 

New question published by babblu arrja is split to a separate thread with the subject MPI cable doesn't communicate anymore.

Best regards
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