Flow stopped through the T1 collimator cooling loop around the same time as a power bump this afternoon.  The problem was narrowed down to failed solenoid valve B1A:T1:SVCOL by comparing coil resistance to other units without issue (~1.0ohm vs 3.6ohm for working units), measured at the T1/T2 PLC cabinet.  Shielding above the T1 package was removed and the solenoid coil was replaced with a new unit.  After replacement the valve works as expected and B1A:T1:FGCOL reading is normal.  I inspected the T1 package while it was uncovered: no leaks observed.