While upgrading the the SRM and SR2 DAC cards to 20 Bit (alog 64384), Marc and Erik noticed we had lost the -18V rail for the analog electronics in the SUS-C8 rack. Found Kepco power supply tripped off. We powered down all electronics and powered supply back on. Unit power on but found the fan had seized and most likely overheated. Unit was replaced. The h1sush56 and h1sush56aux IO chassis were not effected as they are powered off a seperate +24V Kepco power supply.