SLC 5/03 Timed Out Alarms

Today when an operator went to start a piece of equipment that gets infrequent use they got a bunch of time out errors.

Multiple errors saying something similar to this:

Time out reading N20:12 from SLC at Station 1 on driver DH485.

I get multiples of those but with different addresses other than N20:12

This is a SLC 5/03 with a Panelview Plus DH+/DH485/RIO Module.

We are more of a Honeywell site, but we have a few pieces of these stand alone PLC's so I was curious if there was any easy fix or obvious issues. In the end I know we will have to call in a contractor to work on it, but it would be great if I could give them enough info so that they bring the right parts in the first time as opposed to making this a multiple day fix. Any and all suggestions are welcome and thanks in advance.


While googling I did find a thread with a similar/exact issue:
http://www.plctalk.net/qanda/showthread.php?t=116075

They ended up changing a resistor and back pane I think, but I am still interested in other opinions.

I'm assuming you're getting these messages on the Panelview. Sounds like it may be a comms issue between the PLC and HMI. Check for loose cables between the PLC and HMI.

Also check the status LED's on the SLC 5/03 to make sure the PLC isn't faulted etc.

Cycle power to the PLC and HMI if you can.

Correct we are seeing the message on the Panelview. I did unplug and plug the comms cable in. We also powered the unit down and back up and none of that seemed to help.

What should the LED indicators on the SLC look like? Green? Red? Which ones should be on?

On the back of the Panelview where the Comm cable plugs in the light is flashing green

It's very probably a network cabling problem or a damaged device.

Have them take a look at the network status LED on the back of the PanelView; if it's not solid green, there's a network problem.

Check for broken conductors, loose connectors, or isolator modules without power.

Check the DH485 LED on the SLC-5/03 itself; flashing green means it's not connected to a running network, while solid green means that the token is being passed and there's at least one other functional thing on the network.

Also, of course, check to be sure the SLC-5/03 has an operating program in it; do any other elements of the system under the control of the PLC work ? If the program was erased/overwritten you would also see the SLC unable to respond to any commands from the PanelView Plus.

See pg. 87 here for status LED descriptions:


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

So following all the helpful tips here I observed the following:

The Network light on the back of the Panelview is flashing green (never goes solid)

The SLC 5 only has one light it up and that is a solid red on the FLT.

So I guess my question is if the SLC 5 fault is causing the Panelview Network light to flash green or is the Panelview networking issue causing the SLC to fault?

being that the slc led light is solid red, most likely the plc battery is bad and the internal capacitors have also died which means that the plc no longer has the program in its memory.

please look for a program printout or a plc program on a computer, memory stick,...

if I am incorrect, someone please correct me.

james

petro62 said:

So following all the helpful tips here I observed the following:

The Network light on the back of the Panelview is flashing green (never goes solid)

The SLC 5 only has one light it up and that is a solid red on the FLT.

So I guess my question is if the SLC 5 fault is causing the Panelview Network light to flash green or is the Panelview networking issue causing the SLC to fault?

Click to expand...

Most likely the PLC fault is causing the networking issue

The [SLC-5/03] only has one light it up and that is a solid red on the FLT.

Click to expand...

That is conclusive; the CPU has a fatal hardware error. If the LED were flashing, it might have been software (overflow, branching, etc) but the solid red Fault indicator means the CPU has failed a low-level hardware test.

The first diagnostic step I would take is to put the CPU into a known-good chassis to eliminate the chassis or power supply as a source of the problem. Any A-B distributor or field office will have one handy they can let you test with; a flashing red FLT LED means that you're back to a software-level fault.

Check the CPU for an EEPROM plug; if one is present, you have a good chance at recovering the program.

Thank you all for the help. While I wont be able to personally fix this (we don't have the skills or the equipment) I can at least help direct leadership in the right direction to hopefully get a quick solution.

petro62 said:

The SLC 5 only has one light it up and that is a solid red on the FLT.

Click to expand...

You can also try resetting the PLC back to factory default and then try downloading the program back to it, I have a bad power supply cause a solid red about two weeks ago

I have dealt with all sorts of issues like this in the past.You can try some pretty simple troubleshooting steps as I will succinctly outline below, if you find a few minutes (or suggest to the tech).


Please note, removing PLC cards requires pressing on the locking tabs on the front top and front bottom of each card. Also note, don't add/remove any cards with the power on.


Please check/respond to the following:


Troubleshooting power supply issues
----------------------------------------------------------------------------------
1. Is the LED on the power supply on?
2. Is the jumper in the power supply set for the correct voltage (assuming it's a P1 or P2 power supply; if it is another power supply, check this link: https://literature.rockwellautomation.com/idc/groups/literature/documents/in/1746-in004_-en-p.pdf)?
3. Is the incoming voltage correct for the selected/required voltage?
4. Is the power supply properly screwed into the back plane (if the screws are loose, the connections may not be making and so the 5V and 24V the power supply provides aren't being fed properly)?
5. Is there corrosion on the power supply if you pull it out?
6. Do you have another power supply that you can try (sometimes the supply will have the LED lit by have damage on its output side that the LED is useless for)?


Troubleshooting PLC rack back plane issues (simple checks)
----------------------------------------------------------------------------------
1. If you pull out the cards in the PLC rack , do you see any corrosion on the rack circuit board or PLC cards?
2. If you pull out the cards in the PLC rack , do you see any burned components (there are capacitors, resistors, etc. on the circuit board that may have gotten fried by something dripping on it)?


Troubleshooting PLC and PLC cards
----------------------------------------------------------------------------------
1. If you pull out every card in the PLC rack except for the PLC itself, does the FLT LED on the PLC change from solid red to flashing red or off (a bad card can mess everything up)?
2. If you pull out the PLC, are the pins on its connectors to the rack circuit board all straight or are there any bent pins?
3. If you pull out the all of the cards and the PLC, then reinsert the PLC, does the FLT LED change from solid red to flashing red or off (sometimes "re-seating" the PLC solves your problem)?
4. Do you have another PLC that you can try to install (sometimes the processor is just bad)?
5. Can you try to remove the PLC battery, remove any memory card installed on it, and short VBB to GND for 10 seconds to wipe the memory of the PLC and then reinstall just the PLC and check the status of the FLT LED (worked for me once, and only once)? WARNING - The PLC program will be wiped out, so if you have no backup copy of the code, DO NOT DO THIS!


Note to anyone wondering why I would say off for the FLT LED - you can set the configuration of the PLC to ignore missing cards, so it won't necessarily go into a software fault (flashing red) if the cards are not present.


If there is another rack attached to the rack that houses your PLC, remove the ribbon cable connecting them, as I have had a secondary rack power supply go bad and kill everything.


Some of these suggestions may be a little too tricky to do yourself, and based on your previous posts, you may not even want to touch the unit. In that case, please offer these troubleshooting checks as suggestions to the contractor you will call in.


To answer your question regarding the LEDs, you should expect to see the RUN light solid green, the DH485 LED solid green, and the remaining LEDs off. If something is attached to the serial port of the PLC, then the RS232 LED may be flashing green or solid green (I believe it can be solid if set up for DH485). If the program has forces in it (where I/O is forced to be on/off by the programmer), then the FORCE LED may be solid of flashing (depending if the forces are set, but not active). Basically, you can follow the rule of thumb for Allen-Bradley PLCs that red is bad and green is good. The only exception I can think of for you is the power supply - the LED on it is only red and in that case, red is good. There are other exceptions (like I/O card status and indicators on older SLC PLCs), but let's not concern ourselves with those right now.

Thanks everyone for the help. We got the AB tech out here and it looks like the battery & the capacitor that helps store the program were both bad. We put in a refurbished board and loaded the program and did several power shutoffs and startups and everything seemed to work fine from there.