SLC 500 CPU Fault / Faulty Output

DmpTheKiller

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Mar 2012
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Caracas
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Hello everyone!

I'm new to this forum, I'm hoping someone may help me out with some SLC 500 problems I have...

A client has two similar machines each one controlled by an SLC 500 1747-L40A, both machines with similar functionality...

Recently one of the machines has stopped operation due to a failure in a subsystem and they dropped their capacity to half... They're planning on replacing this old controller with a new one (they're studying a project proposal I delivered), probably a MicroLogix 1400, but it takes time and they need to restart that stopped machine quickly...

There is a function of the machine that needs to activate a solenoid to move a plunger latch, then activate an auxiliary solenoid to increase hydraulic pressure in another two-way solenoid valve that also must be activated to drive forward/backward a needle... Long story short, all solenoids seems to be OK (tested separately) and during this process, outputs related to plunger latch and auxiliary solenoid are correctly "enabled" and they're shown enabled in SLC 500 led panel (the small leds that turn on/off indicating enabled inputs and outputs), but the output related to activate solenoid drive forward needle (lets call it SignalX) doesn't get enabled in panel and solenoid never gets the signal (so pressure raises incredibly, an alarm is raised and the process is stopped)...

All the wires have been tested, solenoids tested... Everything is OK... Even with wires disconnected, this output "SignalX" is never enabled in the panel... Internally, the circuitry related to led panel is connected to the outputs of some SMD IC (64 pins or more, don't remember) and also to a darlington IC and then to the relay output...

Since this is the only output not working, the problem must be something related to this "path"... Either the relay, the darlington IC or the SMD IC must be damaged... Maybe the relay or darlington are damaged, maybe not, but it seems that the real problem is this SMD IC that handles about half of the outputs, because the output should be enabled in the panel even if the relay or the darlington IC are damaged... Am I right???

What can I do to try to repair this SLC 500???...

Additionally, I replaced the whole unit with another one they had stored... It was replaced years before for some failure I don't know (I'm new handling these machines) and they don't even know if it is working properly... So I tried to make it run, downloaded the program from an EEPROM delivered by the manufacturer of the machine, and trying to run the processor appears the error code 0012h which means "Ladder program fault" or something like that... What might be wrong with this module??? The EEPROM is OK since it has been used to reprogram other modules before (including the one mentioned previously which is working ok, except for the damaged output)...

Same question... How may I attempt to repair this module???

To finish, there's another SLC 500 around, which has some damage in several outputs... I opened it and it has one of the darlington ICs totally burned... Should I replace that IC extracting one of the ICs from another module (as a desperate solution I may add) and then try to run the module??? I've seriously considered doing that...

One last thing... Consider that the machine is not located in USA and solutions like "replace SLC 500 unit" are already in course, but it takes weeks for used spare parts (the only that may be found for such SLC 500 model) to arrive... Also buying the exact replacement darlington IC is not a quick option, since all electronic component stores sell only through-hole components and some old or very specific stuffs (they have a narrow stock) and buying in digikey takes weeks too...

Please help!!! Thanks in advance!!!
 
I attempted the desperate solution: desoldered darlington IC from one of the modules (the one that always says Error 0012h) and soldered it on another module that had an identical blown IC...

The module started but... Also says Error 0012h!... And I think it's not a program problem because I cleared the fault, redownloaded the program from external EEPROM to RAM using the DTAM and tried to put the processor to "run" state... And this EEPROM is the same used previously in the module with one output damaged and everything else working perfectly...

:S
 
I am at home without programming software (which makes it easy using the help file to look up error codes). I will find some links to manuals for you though. I am sure others will find the meaning of the error code faster though, if any SLC guys are watching this evening.

Paul

EDIT: Go here and download both of these manuals. I expect the error codes are listed (in the 2nd listed pdf) with more info than a handheld programmer.

Okay, maybe not...let me find the better manual for the modular SLC. I think the error codes will be >90% identical...

Well, three times better be the charm... (<- Link to SLC 500 Instruction Set Reference Manual)
 
Last edited:
Okay, so that information is pretty vague and nothing new "The ladder program has a memory error."

Now, the EEPROM has been used successfully on known good fixed SLCs, so I suspect there is some incompatibility between what is stored on the EEPROM and your particular SLC which may have a problem with its memory or some other limitation, like FRN (firmware revision number) or hardware series. I haven't dealt with a great number of fixed SLCs so I am not intimate with any revisions that may have taken place over the years. I can only suggest that you research it at ab.com literature library and knowledgebase.

If I had to wager, I would bet that your suspect SLC has more damage done to it than what you found and repaired.

I think you should find someone nearby with RSLogix 500 who can assist you. Then you can view what logic is really in any of these systems, compare, download...etc.

You then should have no trouble moving the faulty output in the program of the otherwise healthy unit, re-burning it's EEPROM, and ensuring that it "took".
 
Yep... I was starting to think about that different hardware/firmware/revision... I'll check that to see if I get some light... I'll also try to get RSLogix 500 from a friend... Remapping the damaged output is a possibility...

Thanks a lot!
 

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