Jeff Kissel, Elenna Capote
Unfortunately, we just had another TMSX lockloss, after having swapped the TMSX F1/F2/F3/LF top mass coil driver. Jeff and I ripped our hair for a bit checking every signal we could think of. We returned to the FASTIMON signals, and found a discrepancy between them and the MASTER OUT (the digital request to the DAC). The F2 FASTIMON (coil driver output monitor) shows a jump in current, that Jeff and I calibrated to be about a 0.5 mA jump (following the conversion factor of 0.0228 mA/ct from this alog), which we calibrate to be a 50 mV jump in the voltage (following the calibration factor of 9.943 mA/V from this table). However, no such signal is present in the MASTER OUTs, indicating that the DAC is the possible culprit. The usual RMS of the FASTIMON channel seems to be about 0.002 mA, which is about 0.2 mV RMS. Therefore, this is a huge impulse being sent to the suspension, which has a 0.35 Hz resonance (T1200404). We believe this jump is causing the TMS suspension to shake at 0.35 Hz, and the motion is too large for our other slow servos to follow.
We see the jump in the F2 FASTIMON channel but not the F3, for example, in this particular lockloss. Jeff is finding similarly huge jumps in the F2 FASTIMON for some of the other locklosses (he is looking through them now).
Some corroborating evidence that this is consistently happening during (as far as I looked) all of these now-called TMSX yaw excursions or oscillations: Attachment 1 -- 2025-07-29 21:42 UTC (1437860551 lock loss) A repeat of Elenna's plot showing in my formatting the same thing -- the large F2 (uncalibrated) excursion in the F2 FASTIMON where no MASTER_OUT control request is made. Attachment 2 -- 2025-07-27 13:39 UTC (1437277872 lock loss) Attachment 3 -- 2025-07-23 10:49 UTC (1437303004 lock loss) Attachment 4 -- 2025-07-23 03:50 UTC (1437277872 lock loss)
