SR2 Top Satellite Box OSEM Photodiode Oscilloscope Traces
The oscilloscope traces attached show a comparison of the time domain signals between SR2 Top OSEM Photodiode A and SR2 OSEM Photodiode B, as seen from connector J2 "Analog Rack". (We use the satellite box signal and connector naming conventions as shown on D1400098-v1.) OSEM Photodiode A was from the SR2 Top OSEM, the suspect channel. In the images, the upper trace, labeled "1", is from OSEM Photodiode B, satellite box connector J2 pin 2. The lower trace, labeled "2", is from OSEM Photodiode A, satellite box connector J2 pin 1, the noisey channel under investigation.
Two x10 probes were used. The vertical scale factors for images 1 and 2 are 0.200 V/div. The vertical scale factor for image 3 is 0.050 V/div.
Image 1 shows the satellite box as found, all cables connected. Photodiode A shows significantly more noise.
Image 2 shows the photodiode signals with the "Vacuum Tank" cable, connector J1, disconnected. All quiet.
Image 3 shows the photodiode signals with the "Vacuum Tank" cable reconnected to J1. Both photodiode signals now have the same amplitudes. (Note the more sensitive scale factor for image 3.)
An intermitant? A poorly seated connector? Pickup from the SEI CPS 25kHz? Betsy reported that the noise spectrum did not change!
After the above investigation, FIl also powered off the HAM CPS clock synchronizing fanout. The spectra still showed the noise while this was off, although it may have been a little bit reduced. Then, Fil reseated the SAT AMP cable at the feedthru of the chamber which has these channels on it. After reseating the noise was still there. So, we've now tried multiple power switched cable reseating with no luck. Our next tries will be to power cycle the h1sush34 computer (the only one not done today!) and lock closer at the CPS clock sync.
So to recap, there are a few channels which show a "bouncy" type noise spectrum (based on Andy L. tool plots, which I'll ask him to rerun soon) which appeared before or after the power outage:
PR2 M1 T2
PR2 M3 LL
PR2 M3 UL
SR2 M1 T1
SR2 M1 T3
SR2 M1 LF
A scan through all other OSEMs do not show any other OSEMs with this specific noise shape. Attached is the spectra of the still present SR2 noise from today (bottom pane) with some other healthier channels (upper pane).
Continuation of alog 27893.
