jeffrey.kissel@LIGO.ORG - posted 09:59, Thursday 11 May 2023 - last comment - 10:49, Thursday 11 May 2023(69500)
OMC SUS RT and SD OSEMs dead since Monday Morning Jan 16 2023 08:15 am PST (16:15 UTC)
R. Kumar, J. Kissel, T. Shaffer TJ let me know that Rahul found that the RT and SD OSEM sensors have died on Jan 16 2023 08:15 am PST (16:15 UTC). Thankfully, we don't use any alignment offsets on the OSEMs, so this will have only impacted the damping loops. The HAM56 wiring diagram (D1002740) suggests that these two OSEMs are on the same signal chain, and alone on that signal chain, so this should be a relatively easy swap.
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Opened FRS Ticket FRS Ticket 27900
Very interesting find! I've let DetChar know in the chat channel that you've found this, so hopefully they can take a look to see if this is related to our 4 Hz 'bumps' in our spectrum.
- Tried a quick digital offset test to confirm whether the *coils* are dead too, and confirmed that the coils don't cause any current to show up in the corresponding FAST_I_MON coil driver current monitor channels. Coils are dead too - Went out to the racks to see if, for some reason, either the coil driver chassis or satellite amps we OFF. Found OMC TOP Coil Driver S1102660 in U36 of rack SUS C7 OFF - Tried "just" flipping the power rocker switch ON, and it powered on briefly, power indiciator LEDs showed +15 V was getting power, but -15V was not, and within moments the chassis power rocker switch tripped OFF, and then I could no longer turn it back on (the power supply fuse did / is doing the right thing).-15V power leg to the chassis has failed. Filed work permit 11191 to have it replaced. As far as we can tell from the E-traveler, and a quick scan of the DCC for ECRs, we see no indication that the S1102660 driver chassis has been modified from its original design (D1003116), but no guarantees.
Coil driver replaced with S1102657. OSEM sensors are functional again. Drove offsets into RT and SD and confirmed that FAST_I_MONs are reading back current during offsets. FIXED IT. Good to go. Thanks Rahul and Fil!! We'll take some top-to-top transfer functions on Tuesday to super confirm functionality, but we're back in business. OMC RT and SD OSEMs functional again as of May 11 2023 17:40 UTC.