Main hoist brakes would not release. Hoist went down at 8:21 am. Mechanic and electrician informed management that hoist would not be repaired in 30 minutes. Call was made to MSHA hotline at 8:42 am. All electrical and PLC functions were normal. Cleaned brake shuttle spool and check valves. Replaced ""O"" ring seals in brake solenoid. Hoist returned to safe operation at 10:45am.