J. Driggers, R. Short, D. Barker, J. Kissel, R. McCarthy, M. Pirello, F. Clara
WP 12925
FRS 36300

The power supply for the negative rail (-18V) of the SUS-C1 rack in the CER -- the right power supply in VDC-C1, U3-U1 failed on 2025-12-09 22:55:40 UTC. This rack houses the coil drivers, AAs, AIs, and BI/BO chassis -- all the analog electronics for SUS-MC2, SUS-PR2, SUS-SR2.

We found the issue via DIAG_MAIN, which said "OSEMs in Fault" calling out MC2, PR2, and SR2.
We confirmed that the IMC wasn't locking, and MC2 couldn't push the IMC through fringes.
Also, the OSEM PD inputs on all stages of these suspensions were digital zero (not even ADC noise).

Marc/Fil/Richard were quick on the scene and with the replacement. 
We brought the HAM3 and HAM4 ISI -- ISI_DAMPED_HEPI_OFFLINE -- in prep for a front-end model / IO chassis restart if necessary.
Un-managed the MC2, PR2, and SR2 guardians, by bringing their MODE to AUTO.
Used those gaurdians to bring those SUS to SAFE.
- Richard/Marc/Fil replaced the failed -18V power supply.
- While there, the +18 V supply had already been flagged in Marc's notes for replacement, so we replaced that as well (see D2300167).

Replaced failed +18V power supply S1201909 with new power supply S1201944
Replaced failed -18V power supply S1201909 with new power supply S1201957.

The rack was powered back up, suspensions, and seismic restored by 2025-12-09 23:31 UTC. The suspensions appear fully functional.

Awesome work team!