SLC 5/04 Fault and no communication

Hey, I need help. Its urgent.

There is a SLC 5/04 processor connected to NET-AIC via PMO2 serial cable. From the AIC it then communicates to PV 550 and the spare RS232 port is used for programming or whatever.

It was working fine till yesterday until there was a fault in the controller.
Currently Fault is flashing red.
DH+ is constant green.
RS-232 flashes green slow.
No other indication.

To sort out I decided to go online with the controller(if that's possible) with RSLinx (RS232 DF1 Devices). I am using the auto-configure feature. But it's not communicating.

I've attached the latest backup's communication screenshot
Any ideas on how to proceed.

What device are you plugging into when you try to go online?

Have you tried disconnecting the HMI, plugging that cable into your computer, and using the same comms settings that the HMI is using?

If DH+ LED is constant green, then CH1 it is connected to a DH+ network with active partner(s). Can you go online via DH+ ?

CH0 is setup for DH485, so unless the CPU has been completely reset, then you cannot go online via DF1.

To go online via DF1 you may consider to completely reset the CPU, but you will lose the online program if you do so. Is there an EPROM ?

You need a communications adapter such as the 1784-U2DHP for DH+ or 1747-UIC for DH485.

(sidenote: It is messed up that it is a CPU with DH+, and an HMI with DH485. In particular if you do not have hardware to go online via DH+ or DH485).

Check this out:
http://forums.mrplc.com/index.php?showtopic=26935

JesperMP said:

If DH+ LED is constant green, then CH1 it is connected to a DH+ network with active partner(s). Can you go online via DH+ ?

CH0 is setup for DH485, so unless the CPU has been completely reset, then you cannot go online via DF1.

To go online via DF1 you may consider to completely reset the CPU, but you will lose the online program if you do so. Is there an EPROM ?

You need a communications adapter such as the 1784-U2DHP for DH+ or 1747-UIC for DH485.

(sidenote: It is messed up that it is a CPU with DH+, and an HMI with DH485. In particular if you do not have hardware to go online via DH+ or DH485).

Click to expand...

Thanks for the reply,

No, I can't go online with DH-485 or DH+ because of the devices/adapters needed along are not around.

And Yes, you are right. After doing some research I've reached the same conclusion about flashing the PLC. The only reason I was confused was because the client said that he was earlier able to sometimes go online using DF1 driver.

With a short time span at my expense, 2 options left were:
*Go online using an UIC Converter(hardly available these days)
*Reset the controller.

I didn't have the converter handy, so I opted for the obvious. And doing it for the first time but with a little support, I wasn't able to reach a closure after several attempts.

This is what I did-
1) Switched the power down & removed the controller from the rack.
2)Removed the EEPROM(memory module)
3)Removed the battery connector
4) Shorted the pins using a screw driver(2 pins which the battery is connected to) approx. 100 secs
5) Put everything back together & restarted the system.

6) Repeated the above steps over a 10 times.

It's almost like it doesn't want to be flashed.

Is it the only way it can be reset

Please suggest. Thanks.

GTUnit said:

Check this out:
http://forums.mrplc.com/index.php?showtopic=26935

Click to expand...

Thanks,
But I don't have a serial port on my system neither do I have XP. I'm running Win7 64b.

Hope the newest program is actually on the EPROM.

I am just curious about the method you used to clear the memory. You shorted out the battery terminals. I have learned to do this by shorting out the VBB and Ground pads on the back side of the PLC's circuit board. I have never seen one that would not default. Is it possible to have a SLC that will not default?

I use to short the green (or sometimes blue) capacitor.

If there is an EPROM, you should be able to do as you have done and get the CPU back to RUN mode, but you wont be able to go online (because the ERPOM sets the CH0 port to DH485).
If the fault remains, then you are stuck because you cannot investigate why there is a fault.

If you have a backup of the program, you can try to reset and not put the EPROM back in.
Make a new offline backup and change CH0 to DF1.
Also clear the status bits that tells the CPU to load from EPROM.
Download this to the PLC via DF1 if possible.
If that goes well, you can proceed to check everything.
edit: At this stage you will be online via DF1 and can investigate why there is a major error.
If all is well, download the program with CH0 set to Dh485.

Shorting VBB and ground has worked for me, a quick Google search should bring up diagrams of where these pins are on your processor, when doing his make sure you hold the wire (paper clip, or what ever else you have handy) for at least 30 seconds. If the capacitor is really good you might have to hold longer.

I personally dislike using the tips of screwdrivers because the tips are not always in top condition and if you don't hold it perfectly level you can lose connection, especially after holding it for several seconds and your hands are as unsteady as mine.

I use my multimeter set for milliamps, then short the prominent soldering eyes for the capacitor. The soldering eyes are easy to find even in dark conditions, and easy to hold the multimeter pins onto.
I can then follow on the multimeter how the charge is drained from the capacitor.

Well, it has been quite a few years since the last time.

Solved

JesperMP said:

I use to short the green (or sometimes blue) capacitor.

If there is an EPROM, you should be able to do as you have done and get the CPU back to RUN mode, but you wont be able to go online (because the ERPOM sets the CH0 port to DH485).
If the fault remains, then you are stuck because you cannot investigate why there is a fault.

If you have a backup of the program, you can try to reset and not put the EPROM back in.
Make a new offline backup and change CH0 to DF1.
Also clear the status bits that tells the CPU to load from EPROM.
Download this to the PLC via DF1 if possible.
If that goes well, you can proceed to check everything.
edit: At this stage you will be online via DF1 and can investigate why there is a major error.
If all is well, download the program with CH0 set to Dh485.

Click to expand...

Sorry for the late feedback,

As I was not able to reset the controller that evening and with very little time to spare, we had to look at other options.
Luckily they had a SLC 5/05 controller which has an Ethernet port. So I replaced the 5/04 with this and was able to go online through it and found that the fault was in a RTD module. I unplugged it and disabled that slot. Now I was able to go online and run without fault.

The client replaced the faulty RTD card with a spare. And the CPU was running smooth.

Then I again changed the controller back to 5/04 and this time as I was expecting, system was running fine without fault.


Thank you all for valuable advice.