SLC 500 CPU Fault / Faulty Output

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Thread Starter

Diego

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!!!
 
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bob peterson

It is not unusual to have an output fail on SLCs. I would just reprogram the output to a spare and move the wire.

--
Bob
 
Hi:

First you need the program software RSLogix 500 to check this output. maybe there's a condition in the program that avoids this output to enable. If this output is ON in the program try to use a free one and connect there your instrument. I Hope this works.
 
If you have a free output on the unit that's running (and you have the source code and programming software), it's easiest and quickest to move to a spare output. If all outputs are in use, you'll have to either replace the entire unit, or try to repair the bad output.

If I'm reading the manual correctly, the 1747-L40A has relay outputs. Generally, the part that fails is the relay itself. If you have another unit with the same relays, I would try replacing the relay with a known good one. It shouldn't take too awfully long.
 
I actually tried replacing the relay and no solution... I think the problem in this output "path" is not relay or darlington IC, because I even tested both of them in protoboard and they were ok... The problem, I think, is the IC sending the signal to darlington, it's a 80-pin IC (I guess some custom AB processor, because I can't find a datasheet)... Because darlington and relay are ok and also because this signal is wired to processor panel output leds and the led corresponding to damaged output (lets say, Output 10) never turns on (I even tested with load disconnected, to discard some wiring or load problem), so I guess this processor is not sending the signal to darlington and relay...

Remapping the output would be fine if I had the source, but I don't... I don't even have development tools at hand, since the client's policy about these equipment has been to replace the processor when fails, but it's obsolete now and they're having a hard time finding one...

If there's a way of remapping this output without the source code (reading the program from external EEPROM, for example) I'll consider it, but I don't have the dev tools at hand...
 
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

The problem is that I don't have the source code, but I guess I could just read the program from EEPROM and modify the output...
 
Just out of curiosity, how are you getting the error code?

Your local AB distributor may be willing to help you retrieve the source code so you can have someone port it to a current PLC. Or, just get a copy of the software so you can do it yourself. If you're going to be supporting this sort of system into the future, you should probably get the software anyway.
 
I'm getting the error on the DTAM LCD screen...

Yes, I should get the software and development tools anyway, to port the code to a current PLC and redesign some other stuffs... But it will take some time to do and the client needs a faster (temporary) solution... A quick solution (like remapping the output) while a replacement SLC 500 arrives to the country (two weeks? more? :S)... Then, the client will evaluate a proposal I did for the code port and some redesign to include other sensors, all that code port and redesign will be done by myself...

For now, I'll attempt other temporary stuffs (like adding a new panel button to manually control the damaged output when needed), because the delivery time of getting development tools would be the same that waiting the replacement module...

Thanks a lot for your help!
 
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