When Using Dimmer Doubling, I Can Only Control the A Dimmers, not the B Dimmers
Remember when using Express and Expression consoles that the B dimmers are actually DMX512 addresses 257-512. For this reason, the console should be set up to have enough dimmers to cover this range. This menu can be found within the "Setup: System Settings" menu of the console. For ease of use, set the number of dimmers to be the maximum the console supports. Most desks start with min of 1024 and go up form there.