Sony KV-F29MF1 TV, after turning on, can only produce a few seconds of normal audio, when on standby the red LED flashes three or four times and then goes out entering an automatic protection state. However, the raster and image never appear.
Analysis and Maintenance: This model uses the G3F chassis. Not only does it enter automatic protection mode during overcurrent load or overvoltage power supply, but every time it is turned on, it also detects the working status of each circuit on the A board through the CPU. If any fault cannot return the correct signal, the CPU will issue a standby command, making pin 18 output a high level, causing the power circuit to enter standby mode. At the same time, the CPU, according to the fault signals returned by different integrated blocks, makes the standby red LED flash a different number of times to alert the user. Generally, one flash indicates that the memory block IC003 (CA24C04P) has a fault; two flashes indicate the AV conversion block IC201 (CXA1545AS); three flashes indicate the main picture Y/C processing block IC301 (TDA9145); four flashes indicate the RGB separation block IC304 (CXA1587S); five flashes indicate the scanning geometry correction block IC561 (CXD2018); six flashes indicate the surround sound processing block IC202 (TA8776N). However, the information provided by the CPU is not entirely accurate and requires multiple tests, with the most frequent occurrence being the standard. After analysis, the voltage at pin 18 of CPU IC1001 was measured to be 5V, indicating that the power supply has entered standby mode. After turning off the power, short-circuiting pin 18 of the CPU to ground, and then turning it back on, a horizontal bright line of small length appears, indicating that the power supply and line scanning circuits are normal, and the fault lies in the field scanning circuit. The field scan sawtooth wave is provided by IC561 (CXD2018), and the field synchronization signal is provided by IC304 (CXA1587). First, check the voltages at each pin of IC561, finding that the voltage at pin 27 of the reset switch is only 2.5V (it should normally be 5V). Checking its peripheral components reveals that surface-mount capacitor C546 is leaking.
Repair Method: Replace it with a 0.1 or 0.2uF capacitor, and the fault is resolved.
Article Source: http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3682079.