Beijing Sony TV Repair Center, released on September 9, 2011.
Solution: After replacing with a new 0.1F/25V capacitor, the fault was eliminated.
Analysis and Maintenance: Initially suspected loss of brightness signal. Upon turning on the device and carefully observing the image, there were slight changes in brightness when pressing the brightness increase/decrease buttons on the remote control. When increasing the brightness and reducing the color slightly, an extremely dim pale image could be seen, indicating that the brightness signal was not completely lost. This model uses the G3F core, where the IF101 module in the intermediate frequency box is responsible for separating the full television signal into video and audio signals. Then, after passing through the IC201 (CXA1545) TV and AV switching circuit, the YCM301 separates the brightness and chrominance signals from the video signal. Voltage measurements at various points along the brightness signal flow were abnormal.
Upon disconnecting the JW103 jumper to cut off the brightness signal to IC304 and restarting the device, a darker full-color block image appeared, with no response to brightness adjustments. Reducing the chrominance resulted in no screen display, leading to the conclusion that the fault originated from the brightness circuit.
Other circuits affecting the brightness in this core include the ABL circuit and the automatic control circuit for the cathode current of the picture tube. Checking the ABL circuit first, from pin 11 of the horizontal output transformer to pin 26 of IC304 revealed no issues. Further testing showed that the IK voltage at pin 6 of CN703 on the test board had dropped from the normal 1.6V to 0.5V. Checking Q713 and surrounding components found them to be normal. Further checks on Q306 and Q312 revealed leakage from the capacitor C341 (0.1F) connected to the collector of Q312.
Sony KV-F29MF1 type TV, after turning on, exhibits dark light, blurry images, as if composed of color patches.