Barco 500/800/801  

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Focus board

The focus board in the 800 series performs several functions. It contains the sealed focus block that drops the 12 Kv from the quadrupler to about 7 Kv for the focus wires going to the tubes, and the 700 volts or so for the G2 (screen) voltage. The LED’s on the focus board indicate the voltages coming from the SMPS power supply. Any one light being out indicates a fault in the power supply, usually indicating that a fuse is blown. The red scan fail light indicates a horizontal or vertical failure, usually in the power supply, horizontal or vertical boards.

The 6 controls on the focus board are the three screen controls (also called master brightness or G2 controls) and the three focus controls, one per color. The one trimpot adjusts the range of the focus controls. Chances are, if the focus controls are turned all the way to one side, the focus block has drifted, and adjusting the focus range with the trimpot is only a temporary measure, as the focus block will continue to drift. You can’t repair that focus block, you can only replace it.

Once in a while an LED on the focus board will burn out, and thus indicate a fault even if there is nothing wrong with the set. If the projector continues to work, but one light is out, you can ignore the burnt out LED.