Siemens S7-300 going directly to stop mode

I've a Siemens S7-300 cpu (with two DI, two DO and one AI) card. The problem is that all the I/O cards have gone into SF (system fault) with solid red LED (not blinking).

I've tried the following

1. Hard Reset
2. Move the switch on the CPU to stop and then back to run
3. change CPU, change I/O cards
4. Change backplane connectors (those strips which connect two adjacent cards)

The result has been the same. Another thing that happens is that whenever I reset the PLC (hard or soft), it goes directly to stop mode. Normally, after a reset, it used to go directly into the run mode.

So any clues?

Thanks

Whats the diagnostic telling you?

Do you have STEP 7 software?

Have you checked the power supply to the cards?
Have you checked te diagnostics as PeterW suggested?

Nope I dont have the Step 7.

Yes the supply is OK (the cpu is running ok, only the I/Os are in fault)

Have you checked the power supply to the i/o cards with a multimeter?
From the Manual the SF LED can indicate -
Load Voltage Missing
Short Circuit to M
Short Circuit to L+
External Aux. Voltage missing
Internal Aux. Voltage Missing
Fuse Blown
Watchdog time out
EPROM Fault
RAM Fault

In your first post, you state you changed the CPU. In your second post you state you do not have the S7 software.

Did you load the program from an EPROM?

If not, the CPU will appear to go into run. But without a hardware configuration you will have a system fault (SF) because none of the hardware knows where it is or what it is supposed to do.

@Brodin

Yes i loaded the program from the EEPROM by swapping it. Secondly, the CPU is not going into run, it goes directly into stop mode after the supply is turned on to the PLC.

Hi sns,

one more inspection to do is check the first bus backplane connector between the CPU and the first I/O card.

The power supply you checked are OK, there is a good chance that bus backplane communication connector/s are damage or the pins contact havedefect.

Check all them.

Regards

@cagliostro

Done that already and have changed the back plane connectors (all of them) including the CPU and the I/Os.

I got a reply from Siemens and they are of the opinion that it could be that your software is missing/corrupt, am working on that end at the moment but I wanted to ask here that if the software goes corrupt shouldnt the CPU be also in fault?

For info, i've the following cards in the rack

1 CPU315F-2 DP
2 Digital Input (326-1BK01-0AB0)
2 Digital Output (326-2BF01-0AB)
1 Analog Input (336-1HE00-0AB0)

sns said:

For info, i've the following cards in the rack

1 CPU315F-2 DP
2 Digital Input (326-1BK01-0AB0)
2 Digital Output (326-2BF01-0AB)
1 Analog Input (336-1HE00-0AB0)

Click to expand...

So, you are using a Fail-safe PLC, with Fail-safe I/Os; you probably have a fail-safe program in that PLC ( programmed with the Distributed Safety package). Why do I have a feeling that the Fail-safe programming is blocking the restart of your CPU?
The fail-safe program is very touchy; if it is the source of your problem (some form of safety data corruption), I don`t believe that it can be downloaded through the EPROM. It must be recompiled and the safety certificate regenerated, then the program can be downloaded and the PLC restarted.
Without Step 7 (and the Distributed Safety add-on) you cannot read the CPU diagnostics (which would give you indications on the source of the problem, have a look at the Siemens FAQs that follow) or apply a correction.
And a novice with Step 7 + Distributed safety would be lost.
Your best bet would be to contact the provider of the safety PLC/machiune, or at least to find out locally from Siemens who could help you out, probably an integrator with some experience in the matter.

Have a look at these FAQs; they will show you what you would need to read out from the CPU diagnostics just to find out where the problems arised:
http://support.automation.siemens.com/WW/view/en/19183712

http://support.automation.siemens.com/WW/view/en/38068130

Hope this helps,
Daniel Chartier

@dchartier, I'll check up on what you said.

A little update to the scenario

The rack has the following config

CPU DI DI DO DO AI

Initially, all the I/Os except the CPU went into fault.

Now after rewriting the program into the EPROM, the two DIs do not go into SF only the last three do. (The rewriting was done using a special software by this company who provides us support)

Also it is not a blinking SF but a solid one.

It turns out that the MMC card (memory card/eprom) was faulty. Got a new one with the code from the vendor and its working again.

Thanks for all the input guys.

Glag you found a solution.
Glad you posted it here, so othes may profit by your efforts!
Daniel Chartier