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  1. #1
    Junior Member
    Join Date
    Jul 2012
    Posts
    13

    Unhappy Fanuc 18i 749 / 750 Alarm

    Hi All,

    I need some advice. We have a milling machine that came up with a 750 Spindle serial link error. Looking at our controller it has a copper cable between the spindle and CNC controller. We tried a replacement cable and that did not help. We then tried changing the interface board on the spindle drive and that did not help. We then suspected the CNC controller and opted to get specialists in for this . The guy came and tried changing the cable between the spindle amp(JYA2) to the speed sensor on the spindle motor and the alarm went away. His cable was only a test cable and told us our cable was faulty, I ordered the cable and am still waiting for if but my bosses were giving me so much pressure to get the machine running again I went to go see what I could do. I plugged the cable back in and the machine started working. The machine ran for a day and then the same problem. I moved the cable around and it started working again. we then started having the problem more often. My colleges then managed to organize a loan cable from the suppliers. It ran for a day then we started having the Same problem (I was told) When I went to take a look I saw that the machine is giving a 749 Spindle LSI error and it is also coming up with alarm 24 on the drive and then sometimes alarm 750 again. According to the manuals this is a problem between the spindle amp and the CNC controller. I am confused what to look for and what could be causing the problem.

    Can anyone please tell me how to diagnose this?

  2. #2
    Quote Originally Posted by BrendanDixon View Post
    Hi All,

    I need some advice. We have a milling machine that came up with a 750 Spindle serial link error. Looking at our controller it has a copper cable between the spindle and CNC controller. We tried a replacement cable and that did not help. We then tried changing the interface board on the spindle drive and that did not help. We then suspected the CNC controller and opted to get specialists in for this . The guy came and tried changing the cable between the spindle amp(JYA2) to the speed sensor on the spindle motor and the alarm went away. His cable was only a test cable and told us our cable was faulty, I ordered the cable and am still waiting for if but my bosses were giving me so much pressure to get the machine running again I went to go see what I could do. I plugged the cable back in and the machine started working. The machine ran for a day and then the same problem. I moved the cable around and it started working again. we then started having the problem more often. My colleges then managed to organize a loan cable from the suppliers. It ran for a day then we started having the Same problem (I was told) When I went to take a look I saw that the machine is giving a 749 Spindle LSI error and it is also coming up with alarm 24 on the drive and then sometimes alarm 750 again. According to the manuals this is a problem between the spindle amp and the CNC controller. I am confused what to look for and what could be causing the problem.

    Can anyone please tell me how to diagnose this?
    Hi did u find a solution to this ?

  3. #3
    Junior Member
    Join Date
    Jul 2012
    Posts
    13

    Re: Fanuc 18i 749 / 750 Alarm

    Quote Originally Posted by nitishlal View Post
    Hi did u find a solution to this ?
    Hi We found that it was the communication cable between the spindle drive and controller. Unfortunately everyone did not have the correct cable connections. I eventually worked this out and we made another cable that solved the problem.

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