TCL TV audio is normal, but the screen only displays black and white images. Article source: Beijing TCL TV repair hotline http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3701157. Solution method: After replacing R332 and C362, the fault was resolved by contacting the Beijing TCL TV after-sales service hotline.
Analysis and Maintenance: Suspected issues with the chrominance signal channel circuit. This circuit mainly consists of integrated blocks IC301 (luminance delay TDA4565), IC302 (multi-system decoding TDA4555), and IC304 (chrominance control and matrix video TDA3504). Pin 12 of IC304 is the color saturation control terminal, which receives its control voltage from the color saturation formation circuit. This circuit is composed of resistors R615, R603, R332, and capacitors C604, C362. Pin 4 of the microprocessor (PCA84C440) controls the level of the color saturation control voltage applied to pin 12 of IC304. Normally, when the color saturation adjustment button is pressed, the voltage at pin 12 should vary between 1.7V and 4.4V.
Upon turning on the TV, the voltage at pin 12 of IC304 was measured as 0V and remained constant, indicating either damage to IC304 or issues with the color saturation formation circuit. After disconnecting the wiring at pin 12 of IC304 and capacitor C362, the voltage at C362 was found to be nearly 0V. Upon checking capacitor C362 and resistor R332, it was discovered that R332 had overheated, leading to a short circuit in R332 and breakdown of C362.