Model 7002Switch System Instruction Manual - Advanced Test ...

MaintenanceSymptom ⎯ No display:• Defective power supplies. Check voltages.• Blown fuses (power supply boards). Check fuses.• Loose power cables from power supplies to digitalboard.• Loose cable from AC receptacle to digital board.• Blown fuse(s) on digital board (F100 and F101).• Loose ribbon cables from digital board to displayboards.• Defective power switch (digital board).• Defective display boards.• Defective 60V supply (located on digital board).260VAC) and frequencies (47-440Hz), so the fuses shouldnot fail because of incorrect mains voltage setting.If a power supply fails, the instrument will be inoperative.Power supply input and output voltages may be checked atthe connectors at each end of the boards. Table 7-2 lists theoutput voltages that should be available at the digital board.Symptom ⎯ Repeated blowing of fuses indicates a faultypower supply or other boards:• Disconnect the various wiring harnesses or removeboards and check for short circuits.Symptom ⎯ Front panel buttons not working as expected:• Check the display boards (run BIT).• Check for broken or damaged contacts on keyboard buttonmembranes.Symptom ⎯ Display tests run but show incorrect characterson the VFD display:• Change display board.7.9.3 Power supplyThe Model 7002 power supplies will resist problems affectingconventional power supplies. The power supplies automaticallyadjust to a broad range of mains voltage (90-7.9.4 Backplane boardsThe backplane boards interface plug-in relay cards to thedigital board. If communication through the backplane boardis faulty, check the cards and the condition of the card edgeconnectors on the backplane boards.Symptom ⎯ Incorrect identification of relay cards pluggedinto backplane:• Move the affected relay card into the other backplaneslot. If it is correctly identified, suspect the backplaneboard. If not, suspect the relay card.Symptom ⎯ Test circuit configurations not functioningproperly:• Defective or improperly seated relay cards.• Defective backplane board.Table 7-2Power supply checksTest point Output voltage Tolerance Rated load Ripple/noise Reference toJ1011-1 +14.6VDC ±5% 1.67A 100mV Digital groundJ1011-4 +6VDC ±3% 2.5A 50mV Digital groundJ1012-4 +6VDC ±3% 2.5A 50mV Digital groundNotes:1. Tolerance is measured with output at 60% rated load.2. Ripple/noise is measured by using a 12-inch twisted wire terminated with a 47µF capacitor.7-17