image degradation and possible improper diagnosis as shown in fig2 and in greater detail in fig4 erase lamp assembly 88 includes twelve fluorescent lamps 88 1 to 88 12 arranged in pairs each pair of erase lamps are electrically connected in series to a ballast 102 thus erase lamps 88 1 and 88 2 are connected in series to ballast 102 1 erase lamps 88 3 and 88 4 are connected in series to ballast 102 2 erase lamps 88 5 and 88 6 are connected in series to ballast 102 3 erase lamps 88 7 and 88 8 are connected in series to ballast 102 4 erase lamps 88 9 and 88 10 are connected in series to ballast 102 5 and erase lamps 88 11 and 88 12 are connected in series to ballast 102 6 an alternating current ac source 104 supplies ac current to erase lamps 88 1 to 88 12 through ballasts 102 1 to 102 6 ac current is sensed between source 104 and ballasts 102 1 to 102 6 by electromagnetic field current sensors 99 1 to 99 6 a current sensor 99 1 to 99 6 senses the electromagnetic field produced by current in a conductor surrounded by the sensor an exemplary current sensor is type ctl 6 s distributed by u r d america inc laguna niguel calif detect circuits 100 1 to 100 6 are respectively connected to current sensors 99 1 to 99.