03feb05 td12 trouble


        On 03feb05 around 8am, td 12 began making a loud noise on the speakers in the control room. It sounded like hard rain (but it was not raining). After a few moments the motor went into foldback. A little later we stopped the tiedowns. Something similar occurred to td12 on 31jan05 at 23:20 pm. At that time it also went into foldback.

    Plots were made of some of the measured values of the 3 tiedowns covering 8:27 to 8:33 on 03feb05. The tiedowns are color coded so that td12 is black, td4 is red, and td8 is green. The tiedowns were turned off at 8:30 and turned back on at 8:31:38.
     The plots during the problem show:

    Td 12 is definitely having problems. If the commanded velocity read back is valid, then there must be something wrong with the d/a, signal conditioning board , or the little star. Unfortunately this signal is often corrupted by rfi.  The little start is probably ok, since the other values seem reasonable (for the requested read back velocity). If the commanded velocity to the amp is really what we see in the commanded read back, then the PI loop will cause the other parameters to change as they do.
    When the tiedowns are turned off, all of the signals except the command velocity read back go to zero (as they should). So my first guess is to replace the dac and signal conditioning board.

    This problem has occurred twice (that we know of ) in two days so it is intermittent. We may have to way a while to see if the changes really have fixed things.

processing: x101/050201/tdprob03feb.pro