Should you be able to talk to a SLC5/02 when it has a memory module fault?

[strantor]

Last night I was trying to revive an old derelict machine after a slumber of many years. I couldn't connect to it with 1747-UIC cable from plccable.com (geniusintraining). I tried the UIC devices driver and also DF1 driver under KF3, still no luck.

I assumed it would have lost the program, but apparently, according to the manual the memory module is actually bad, not just missing a program. Power light and fault light both stead ON.

I have a new memory module on order but I'm worried once I get it, I still won't be able to connect to the PLC. Should I be worried? Is this specific failure mode the reason for my being unable to communicate with the PLC?

 

[glenncovington]

Can you remove the memory module and see if power cycling clears the fault.

 

[strantor]

Can you remove the memory module and see if power cycling clears the fault.

I did that last night, in accordance with the manual. Removed memory module, put processor back in, same combination of status LEDs. This points to bad memory module. Put the module back in, put processor back in, no change. (powered off between steps).

After that I went a step further per some suggestion in an old thread that I read here, to remove the processor, disconnect the battery, and short VBB to ground. I assume that means the pins where the battery connects. (powered off between steps). I did this twice; once with memory module installed and once without, no change.

 

[Operaghost]

I would probably try to revive the controller with the memory module removed. Just to eliminate that as a possible source of the problem. The module is not required for the CPU to operate. It is just a backup beyond what the battery can do. So not sure a new module is going to make any difference if we can't get it talking with the old module removed.

The 5/02 shouldn't need the short VBB to ground trick. That was for the 5/03 and newer as a means to dissipate the power from a capacitor and thus reset the module. The 5/02 doesn't have this same type capacitor, so removing the battery, if it was good, does the same thing for those controllers.

The solid red CPU light usually means the processor is dead. If it simply didn't have a program loaded it would be flashing red. If the CPU is still good, it is probably reset back to (Data Highway) DH-485 node #1. You'll need to make sure your computer isn't also using node #1.

We can normally still communicate with a faulted controller. But a dead controller is another issue. Fortunately you can pick up a replacement pretty inexpensively (checking on eBay). Although a 5/03 is probably about the same price, and I would prefer that over a 5/02.

OG

 

[strantor]

I would probably try to revive the controller with the memory module removed. Just to eliminate that as a possible source of the problem. The module is not required for the CPU to operate. It is just a backup beyond what the battery can do. So not sure a new module is going to make any difference if we can't get it talking with the old module removed.

The 5/02 shouldn't need the short VBB to ground trick. That was for the 5/03 and newer as a means to dissipate the power from a capacitor and thus reset the module. The 5/02 doesn't have this same type capacitor, so removing the battery, if it was good, does the same thing for those controllers.

The solid red CPU light usually means the processor is dead. If it simply didn't have a program loaded it would be flashing red. If the CPU is still good, it is probably reset back to (Data Highway) DH-485 node #1. You'll need to make sure your computer isn't also using node #1.

We can normally still communicate with a faulted controller. But a dead controller is another issue. Fortunately you can pick up a replacement pretty inexpensively (checking on eBay). Although a 5/03 is probably about the same price, and I would prefer that over a 5/02.

OG

Ok well that's bad to hear, but good to know. I guess I'll need to cancel the order for a memory module and order a new processor instead. I did try to communicate with it while I had the memory module removed, no luck. Thank you.

 

[strantor]

You were correct. The processor had the same fault and still would not communicate after replacing the memory module with a brand new one. The memory module had already shipped when I acted on your response and ordered a new processor card, so I decided to go ahead and try the memory module first; didn't fix it. So I put in the new processor and was in business, but when I tried to copy to eeprom, it said it was full despite the program being only 268 words. So I put in the memory module I thought I wouldn't need, and now back to 100%.

Thanks for the help!