Note: The illustrations show the replacement of the chuck valve. The tailstock valve replacement is the same.
Press [POWER OFF]. Set the main circuit breaker to the OFF position. Lock the main circuit breaker. Use an approved lock with an approved safety tag.
Remove the valve  from the valve block with a crow foot wrench . Before you install the replacement valve, turn the main adjustment knob  on the adjustment valve counterclockwise until it stops.
Install the replacement adjustment valve with the crow foot wrench . Leave the screw on the locking jam nut  loose.
Unlock and turn on the main circuit breaker. Press [POWER ON].
Release [EMERGENCY STOP]. Press [RESET] to start the Hydraulic Power Unit (HPU).