The result of the precise inspection for the PMC servo board for the 40m was done.
The record, including the photo of the board, can be found at https://dcc.ligo.org/D1400221-v2
- I found some ceramic 1uF caps are used in the signal path. They have been replaced with film caps by WIMA.
- In later measurements with the openloop TF measurement, it was found that the notch frequency (14.6kHz) was off from the a sharp PZT resonance at 12.2kHz.
I replaced the combined caps of 1220pF to 1742pF. This resulted nice agreement of the notch freq with the PZT resonant freq.
Past related elogs:
SRA-3MH mixer installed in 2009: http://nodus.ligo.caltech.edu:8080/40m/1502
R20 increased for more LO Mon gain: http://nodus.ligo.caltech.edu:8080/40m/10172 |