Black and white picture and sound is normal, no color, show that the fault is mainly color decoding circuit. Measuring IC501 {} 34 feet voltage, 5.5 V (normal is 8.8 V), decolorization identification circuit has been open. Resistance will be 20 k Ω jumper between {25} and {} 34 feet, close the decolorization recognition circuit, still no color. Problem may be} {26 feet without chroma signal input or native subcarrier crystal oscillation stop vibration circuit. Check the crystal vibration X501 has leakage damage, renewals, still no color. Check} {26 feet peripheral components, found C503 (56) pf capacitor serious leakage, after replacement, color returned to normal.4Ebservice manual download site