LG 50PQ30 Training Manual page 131

50PQ30 SERVICE TIP SECTION
50PQ30 SERVICE TIP SECTION
Floating Ground checks must be made from Floating Ground. Use any pin on P204, P203, P205 or P208.
SYMPTOM:
The panel indicates a brief flash during start up, then "No Picture" symptom.
CHECKS:
1. Z-SUS does not produce a correct signal. (All voltages check normal except 17V).
2. Y-SUS does not produce a correct signal. (No negative portion).
3. On Y-SUS: 17V starts off at 17V then very quickly drops to 5V.
4. Floating Ground 5V and 15V are not produced. (See pages 60~61 for more details).
5. Removing all connectors on the Z-SUS board (Except the panel connectors) does
not change test results.
6. Removing Y-Drive boards cause all voltages to return to normal.
Including the Y-Drive signal checked on the right side of C213.
7. Reconnecting all connectors on the Z-SUS board shows it is not creating a
correct waveform. Just spikes. (17V now stays up).
8. Using the Diode Checks for the Y-Drive boards do not indicate a problem.
(See pages 67, 70, 71 and 74 for more details).
FIX:
Replacing the Z-SUS board fixed the problems.
TIP:
131 131 November 2009 50PQ30 Plasma