text: <s>[INST] Problem with SERCOS interface on Ultra3000 Drive. We have a control system that consists of 4 Ultra3000's communicating with an Allen Bradley PLC via a SERCOS fiber optic link. Ever since the initial startup of this unit we have had intermittent communication errors. Well, today they became much less intermittent and more permanent, we could only keep communication established for about 10 minutes in every hour. Each one of these drives are connected to the SERCOS in series to each other. It was obvious therefore to find out where the communication ended. I have no way to test the quality of or the data integrity of a fiber optic link, I can only use my eyesight to verify that there is light emitting from the SERCOS link at whatever point that I remove a cable. It was obvious using this method that the signal was entering a certain drive in the string, and in fact was being acted upon since the communication light was green, but it was not exiting this drive and entering the next one in the string. The red light was not emitting from the output of this card, so that eliminates the next fiber optic cable as being the problem. Also, if I remove the cable from the input of the bad drive and install it in the input of the next drive in the string, the rest of the drives from that point on establish communication again. So, obviously, the SERCOS interface card is defective in that drive. The question is, What has been the resolution of this problem? If you ran into this, was it just as simple as maybe the card is not fully seated into the connector in the drive? Remember, this problem is intermittent, it comes then it goes. I actually observed the output starting to work, then not work visually several times while the output cable was removed. Or does anyone know what specific component on the board may be defective? I have not disassembled the drive yet to see what components are there, but assume there must be an optocoupler I.C. of some sort that may be getting spotty? Or possibly something as simple as a poor solder joint? The simple answer is obviously to replace the card, but the customer is coming in Monday afternoon to observe the unit we are using this control system on run, so it might be quicker to source the individual component locally. Thank you for your help. [/INST] Is the drive with the problem still under warranty? I have never messed with the internal hardware of the SERCOS interface on the Ultra 3K but I have had this problem before. I just had the drive replaced. By the time you mess around with troubleshooting at the component level, you could just get a new drive and be done with it. I don't know what the urgency for this application is, but the drives aren't that expensive. \\n </s>