From time to time we receive calls stating a large commercial Stewart screen won’t operate. In many cases the on-board circuit breaker has tripped causing power to be interrupted from the controller. A simple reset of this circuit breaker can reactivate the AC power and the screen will start to function normally once again. You can locate this circuit breaker switch on the backside of the unit’s electrical enclosure (see photo below). This breaker will trip if there is not sufficient AC power available at the time someone has sent a command to the screen.

On many occasions the third party control system can send false signals to the screen’s control board. For example if an erroneous “latched” command has been sent, the screen will not operate. So the best way to trouble shoot this is to pull the 3^rd party “common” connection from the system and test with just the 3 button wall switch. If the screen starts to operate normally with the wall switch, then the third party control system is causing the problem.

You may also test the screen with the control board’s test buttons. Open the unit’s electrical box and press the small square buttons in the center of the control board. If the screen doesn’t correctly respond, disconnect the “white” common control lead from pin# 4. If there is a problem on the switch leads the screen will operate correctly. When you reattach the switch lead and find the problem returns, then you know the issue is with the switch leads, switch or 3^rd party control network.

The control boards rarely fail but if that is the case the test buttons will not illuminate nor will the motor activate. In this situation the control board itself has gone out and needs to be replaced. See the photo on the next page of an actual AMX control board (older units). Notice the (2) white push buttons in the middle of the board.   

 The black square button is the unit’s circuit breaker

The gray P2 switch terminal will have the four switch wires connected to pins 4 – 7 only. If needed, remove the “common” lead from pin# 4 to test the screen without any switch connections.

The (2) white square push buttons will activate the screen up or down. The test button’s red LED’s will illuminate when the motor is running. These LED’s will stay lit for up to 90 seconds at which time the internal power will shut off to the output relays. Do Not change the DIP switches near P2 terminal as this will cause damage to the control system.