As always, proper equipment grounding practices should be used. It is important to have dedicated ground wires from projectors, light dimmers, racks, etc., running back to the electrical distribution panel. Make sure these grounds are solidly connected at all connection points. Failure to do this may result in noise pickup from light dimmers or other equipment. If you use wire nut connections at any point, make sure they are very tight. Even a slightly poor connection can cause much noise. The LED soundheads used in the CHRISTIE projectors have unused ground pins available on the header pin connectors on the soundhead preamp board. It is necessary to connect the SHIELD of the solar cell cable to one of these ground pins. The SHIELD should also be connected to one the ground pins on the SMART processor. This is in contradiction to the usual practice of cutting off the shield at the projector end of the cable. However, connecting the shield in this way will result in the quietest performance in both normal and backup modes. Please note: the ground pin on the soundhead preamp board is not connected to the projector ground, but is connected to the preamp circuit ground. Connecting to the projector ground will probably cause a hum-producing ground loop. The LED soundheads produced by Component Engineering have the ground pin connected through one of the circuit board mounting screws. Several projector manufacturers are now shipping the LED soundheads on their projectors. These soundheads offer vastly superior performance to the traditional exciter lamp and solar cell setup. In order to realize the improved performance with SMART equipment, some precautions must be observed in the connection between the soundhead and the processor.As always, proper equipment grounding practices should be used. It is important to have dedicated ground wires from projectors, light dimmers, racks, etc., running back to the electrical distribution panel. Make sure these grounds are solidly connected at all connection points. Failure to do this may result in noise pickup from light dimmers or other equipment. If you use wire nut connections at any point, make sure they are very tight. Even a slightly poor connection can cause much noise.
The LED soundheads used in the CHRISTIE projectors have unused ground pins available on the header pin connectors on the soundhead preamp board. It is necessary to connect the SHIELD of the solar cell cable to one of these ground pins. The SHIELD should also be connected to one the ground terminals on the SMART processor. This is in contradiction to the usual practice of cutting off the shield at the projector end of the cable. However, connecting the shield in this way will result in the quietest performance in both normal and backup modes. At this point, CHRISTIE does not have a wire in the wiring harness which connects to a ground pin. Please note: the ground pin on the soundhead preamp board is not connected to the projector ground, but is connected only to the preamp circuit ground. Connecting to the projector ground will probably cause a hum-producing ground loop.
The preferred method of connecting to the ground pin is to contact CHRISTIE and order a Crimp Connector , CHRISTIE Part # 524900-081. Attach a 6" to 8" length of wire per CHRISTIE’s instructions and insert the crimp connector into the middle position on the power connector socket. Then attach the free end of the wire to the shield of the solar cell cable.
As an alternative connection method, strip and tin a piece of 24 Gauge or
smaller stranded wire and make a small loop on the tinned end which will
slip over the middle pin of the power socket on the soundhead preamp.
Use long nose pliers and push the loop of wire all the way to the back
of the pin. This is important to do properly so that the power connector
will seat all the way on the pins. Carefully solder the wire on the pin.
Do not use excessive solder. Be certain the wire is not touching either
of the other two pins. Tug lightly on the wire to make sure the solder
connection is tight.
The LED soundheads produced by Component Engineering have a ground terminal available which may be used if necessary to connect to the solar cell cable shield. The ground pin is connected through one of the circuit board mounting screws to the metal case of the soundhead preamp. It may be necessary to remove this mounting screw to eliminate the circuit ground to projector case ground connection. Try it first with the screw in place. If any hum results, try removing the screw, and if the hum level improves or goes away entirely, leave the screw out. There has been no extensive field experience with the Component Engineering unit, so your particular situation may not have any problems. However, if you experience hum and/or buzzing in either Normal or Backup mode, try this solution.
Remember, there may be other grounding problems which can also cause hum or buzzing. Our Technical Support Department is available to help you with this or any other problem. Please call us at 1-800-45-SMART or 1-800-457-6278.
