Troubleshooting - Sony KZ-32TS1U Training Manual

FIGURE 27-4 - COMPLETE POWER BLOCK ASSEMBLY

4. Troubleshooting

Defect – Unreliable backlight starting
As the gas discharge tube reaches the end of life, the most common symptom is unreliable starting at power ON,
especially when the lamp is cold. Replace the lamp.
Defect - No backlight repair procedure
The lamp will not turn ON because of a defective:
•
Lamp
•
Power block board (no HV)
•
Control engine (M board – no turn ON signal).
•
Fusible resistor(s) on the power supply G board.
Concept: When the backlight bulb / lamp reaches the end of life and does not ignite, the internal resistance
across its two terminals remain high (open circuit). This causes the HV to climb to 25kV and arc across the spark
gap device (G1) on the Powre block (proving the Power Block and controlling M board are working). The HV
arcing makes an audible frying sound and light is visible. The HV arcing lasts two seconds, stops for five
seconds and repeats until the TV shuts down in three minutes.
Troubleshooting procedure: If the Power Block arcs, the bulb is either defective or not plugged in. No arcing?
Measure the HV control signal input to the white wire of the 3-wire connector on top of the Power Block. If this
CTL input voltage is correct at 5Vdc at TV turn ON (within two seconds), the Powr Block or power supply board
fuses are bad. If CTL is 0Vdc at turn ON, the controlling M board is bad or one of the Fans is not rotating (no fan
causes no lamp ON and shutdown). See the Fan Control Fan Troubleshooting in Chapter 26 or just check the
self-diagnostic Chapter 16.
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27. Grand Wega Lamp Control