Mercury Arc Lamps "J&L Projection":

We have had much discussion as of late regarding the testing and verifying of mercury arc bulbs. We have complied this procedure to check the run circuit to verify its operation.

A qualified Factory Trained and Authorized Service Technician should perform this operation

  • Remove the Lamp house and Mercury arc bulb.    
  • Put the red lead on the center post and ground on the outer rim of the lamp socket.
  • Activate the lamp house safety switch "depress the micro switch"
  • Voltage reading should read between 70 to 85 volts DC
  • Activate start button
  • Voltage should rise to between 400 and 480 volts DC


If you have performed this operation and confirmed voltages and your mercury arc bulb does not start or stay lit is safe to say that your bulb is bad. If either of the voltages is out of spec you have a run circuit electrical problem.

Mercury Arc Lamps: Anytime a mercury arc lamp is replaced use a volt meter and a DC amp meter and connect as shown in the original electrical schematics. Adjust R-17 for 250 watts, +/- 2 watts. This will insure the best performance and life from the lamp. This is also a good time to make sure the mercury arc power supply is clean and the fan is in good working order.

Fiber Optic Edge Sensing: Periodically check light levels for your edge sensing. Make sure all the optics are clean, lamps are properly aligned and verify light levels. Even though the bulb maybe lit it may not be putting out the lumens that it did win it was new, If your lumens are weak it maybe a good time to go thru and check, alignment and replace the optical comparator bulb.