There are two thoughts. Both depend on your viewing habits. First, no "lock out" exists. But you could leave your host on the bad channel and it won't be used. Also you could preset the other tuners to the channels on your To Do List. The preset is better since a TiVo will always use a tuner on the channel already on a channel if it exists. Leaving a tuner on the dead tuner will not work for long since the tuner on a channel longest (time since tune start) will be first chosen, other factors being equal.