LG 50PQ30 Training Manual page 8

Basic Troubleshooting Steps
Basic Troubleshooting Steps
• Define Look at the symptom carefully and determine what circuits could be causing the
failure. Use your senses Sight, Smell, Touch and Hearing. Look for burned parts and check
for possible overheated components. Capacitors will sometimes leak dielectric material and
give off a distinct odor. Frequency of power supplies will change with the load, or listen for
relay closing etc. Observation of the front Power LEDs may give some clues.
• Localize After carefully checking the symptom and determining the circuits to be checked
and after giving a thorough examination using your senses the first check should always be
the DC Supply Voltages to those circuits under test. Always confirm the supplies are not
only the proper level but be sure they are noise free. If the supplies are missing check the
resistance for possible short circuits.
• Isolate To further isolate the failure, check for the proper waveforms with the Oscilloscope
to make a final determination of the failure. Look for correct Amplitude Phasing and Timing
of the signals also check for the proper Duty Cycle of the signals. Sometimes "glitches" or
"road bumps" will be an indication of an imminent failure.
• Correct The final step is to correct the problem. Be careful of ESD and make sure to
check the DC Supplies for proper levels. Make all necessary adjustments and lastly always
perform a Safety AC Leakage Test before returning the product back to the Customer.
Define, Localize, Isolate and Correct
8 November 2009 50PQ30 Plasma