Slc 5/05

Have a problem with a 1747-552 with 28 modules attached, after every power cycle it faults out and will only respond to a program download, red fault light is solid red in run position but flashes when switched to program, batt light is not lit but have ordered a spare anyway and will replace, have replaced the PSU but no change! so whats left? CPU and/or the backplane? this system has been running for 10 years without this error occuring, but I will add that this occured after a stormy weekend that also fried our sat modem! any ideas? and how do I get a fault log if it will only let me do a download which clears the errors?

hmm..what comms are you using to try and go online to see the fault?

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1747-um011_-en-p.pdf

right around page 149 could help you

Thanks Robo, will check power supply next, this unit is supplied via a transformer 240 to 120vac why they did it that way don't know, comms is via ethernet.

If the Fault LED is flashing when you are in Program Mode. You should be able to go Online and see what the Fault is. If that doesn't work, try Uploading the PLC Program, and reviewing it Offline. If you are able to Download the PLC Program using the Ethernet Port, it seems like everything is not lost, since it must still have an IP Address.

Stu....

I had a similar problem with a SLC 5/05 after a nearby lightening strike. Same symptoms & I could only get comms via the RS 232 port with a null modem. The program was "gone" & had to be downloaded. The processor began to repeat the fault every 24 - 36 hrs. The only cure was a new processor. I sent the original to Allen Bradley and they pronouned it "Beyond Economical Repair" .......Bob

Grounding.

Our NJ plant had the same problem, two 10 slot chassis SLC would fault whenever they would turn off the power or have an outage. Rockwell had suggested a number of things, including making sure the chassis and panel were all properly grounded (ground wire on chassis, not just relying on backpan connection, etc). They tried everything else but poo-hooed the grounding. Eventually they asked me for help on one of my trips to the plant. I noticed that there was no ground wire pulled to the control panel. I pulled a ground over from a nearby panel and put ground wires on the chassis. They never had another problem. Your problem could be something else, but if you haven't followed the grounding instructions in the SLC manuals then do that before you spend a lot of money.

Thanks guys for the suggestions, will check the earthing and also have ordered spares to hold anyway as the system is 10 years old, only have had to replace a P4 and one module over the last 5 years so it has been pretty reliable so far! FYI price here for the 1747-552 is $4298

You can buyer 1 on ebay for cheaper. Also repair is only around $850. http://www.ind-concepts.com/Repair.htm

Just an update! after another weekend and a power cycle the CPU finally wouldnt allow a download so replaced the CPU module and everything now back to normal, so it seems the stormy weekend also did some irreparable damage to the SLC5/05!

Glad to hear you got it sorted out Ray. Thanks for getting back to us.


Stu....

Just a word of warning.

I had a system with almost the exact same symptoms. Changing out the processor seemed to fix the problem. 6 months latter the symptoms came back and we lost another processor, and then one more time.

The power supply had also been changed a few times before I got involved. We finally changed out the power supply one more time plus the rack and never had another issue. The power supply circuit board was noticeably discolored at the bottom near the back plane.

You might pull the power supply out and inspect it when you have it down sometime or just change it and the rack out for insurance purposes.