Siemens S5-95U issues, been working for years and now stop light lit

Story goes we have a rather huge milling machine down in the mechanics shop that they were using for the last 13+ years and now just this week it won't run. So, of course they call in the electricians who do what electricians do best... shotgun troubleshoot. After a few days of this they called me in(electronics technologist) to come down and take a look... yeah they have wires pulled, fuses yanked, jumper cables installed, and a German manual they claim they can't understand the schematics.

15 minutes I figured out the German schematics, showed them what was causing them grief, got them to put everything back in order and then trace back a few sets of wires that were controlling the problem relay, and inside the other cabinet they never checked was this S5 controller with the STOP light lit so the program isn't running. I downloaded the manual and it says "PLC in STOP, Red LED is LIT = PLC Malfunction, Use programer to execute interrupt analysis"

Ok, so somethings gone screwy with the PLC. This device has been in service since I believe '91 or '96 so a rather long time so it's not a code error, it does have a eprom I believe according to the manual, memory module 375 EPROM 8Kbyte, the battery was completely dead so changed it out and tried to start up the PLC again but basically everytime you switch it to run mode the RUN light lights up for about a second then it switches over to the STOP light again

So, what can a guy do to try and find a solution? We don't have parts, we don't have the Step5 software, we don't have the crazy 232 to 4-20ma cable... I'm sure push come to shove the company would buy it all but I'm curious if there are some tests I can do before I go that route?


Rundown of the PLC according to the manual I have

SIMATIC S5-95U
Memory Module 375 EPROM, 8Kb
Buffer battery LI
Bus Module with crimp connection
Digital I/O 482
Digital Input 421
Digital Output 451

OK without diagnostics you may struggle!

Main point is processor is running, then stopping, so it sounds to me like it is encountering something that it doesnt like in the program. I know you said program was on EPROM, but have any changes been made in RAM? 95U copies from EPROM to RAM at power up if there is no battery.

Try

Removing battery
Turn power to CPU off
Wait a few minutes (time for a cup of tea if you are this side of the atlantic!)
Turn Power back on
Replace battery

Order of above is important.

Program will reload from EPROM

If this doesnt sort it you will need someone with S5 software and a cable to investigate the ISTACK which is where the PLC stores what it was doing when it went into stop, and the cause of the stop.

I would do it but the air fare and travel time might be a bit more than you are prepared to pay!

It may be that whilst most of the program is on the EPROM, the Data Blocks may not have been. In this case you will need a programming device and a copy of the program to put back the Data Blocks (to be kept in ram by the battery).

I too would be only too happy to sort it out for you but you may be able to find someone closer for fix it for you.

Nick

P.S. What is the exact part number of the Eprom?

Man all you guys from across the pond want a free trip out here


Anyway, Mike the suggestion worked! I honestly thought we had tried that before because the electricians like I said found the LI battery was completely dead so they removed it and got a replacement. I thought though they had the power to the machine shut off since they were working inside the cabinet but instead they pulled the battery out, put the new one in while there was still power to the PLC

So, technically the machine never lost power so kept the currupt program running, and now that it has a new battery installed when we shut off the power again it would keep the same program running.

This time we pulled the new battery, shut it all down, cleaned up a bunch of the wiring and put the covers back on etc, then I put the switch back into the stop position, fired up the PLC, the red light flashed on/off a few times then went solid, switched it back to run and away it went!

So yeah, score one PLC.net and also Britain! I think everyone around here was pretty impressed I was able to get in contact with someone across the globe who pointed us in the right direction for a fix

Manglemender said:

P.S. What is the exact part number of the Eprom?

Click to expand...

Not that it likely matter anymore, 6ES5 375-OLA15

BigTom209 said:

Not that it likely matter anymore, 6ES5 375-OLA15

Click to expand...

If you wish to support this PLC without major cost outlay

http://www.process-informatik.de/

Go to this web site and download the demo STEP5 & STEP7 PG2000. This will give you a demo package that can get you online to troublshoot in 10 minute intervals.
You will also need the RS232 to 20ma CL cable Siemens part #
6ES5-734-1BD20 and a true 9 pin serial port. The siemens cable is 25 pin, so a 25 pin male to 9 pin female adapter is also needed

The problem is usually DB1, when you get a new s95U wit will not go to run.
You have to remove the battery, switch on, go from stop to run twice then when in run mode insert the battery, the problem is that DB1 is generated by the plc with default cofiguration parameters in it for analogs, time ob's comms etc.
if the battery is flat then powering down will lose this db.
so even if the eeprom loads into memory usually DB1 is not put on the eeprom by the programmer as you would need to upload from plc to disk then ensure it is programmed onto eeprom.

Just a point in case anyone has similar problems in the future, if DB1 is the problem the the processor will not enter run at all. Same applies to the majority of harware errors.

So if the run light goes green and then back to red problem is usually with the program. Corrupt, or missing data blocks are the commonest errors

Hello guys, i'm sorry bringing this thread up but I looked at almost whole internet and found nothing about what it is happening with my PLC.

It is a S5-95U 6ES-8MA03.

The red light is on and when I switch it to run the green light lits together with the red light.

I tried everything you posted here and the same keeps happening.

When the battery is removed and the it is powered up, the red light flashes like crazy. So it is copying the program.

I dont have the rs232-20mA cable.

I think it is something really stupid that I am missing.

This PLC has hanged several times, but not this way.

Please help me. It is running on a Plastics Injector and is the only machine I have.

Thx a lot.

Just a note, we had one S5 (RIP) that got its memory corrupted few times that screw up the program.