Observe the machine gray image is not clear, only fuzzy color images, adjust the brightness and chroma control function, but to adjust the contrast control without any change. Fnqservice manual download site
 Fnqservice manual download site
Maintenance experience has shown that this is typical of the lack of brightness signal failure. The reason general maintenance switch is open, or brightness delay line to ground, the short-circuit. Because the machine have a maintenance switch, the first check brightness delay line and around DL301 related circuit, but did not see abnormalities. Fnqservice manual download site
 Fnqservice manual download site
Check the color decoding block IC501 (HA51339SP - 3) about the terminal voltage, including 19} {~ {and} feet generally low voltage, 3.6 V, 2.3 V, 1.4 V, 2.2 V, 8.0 V, and {4} feet high voltage is 7.6 V, the waveform measurement {4} feet, only sync signal, and no video signal (see chart). This shows that the fault is caused by lack of luminance signal. Fnqservice manual download site
 Fnqservice manual download site
 Fnqservice manual download site
To identify IC501 is normal, the alternative method to check the voltage simulation. With a 100 k Ω adjustable resistance, between its two ends respectively received a + 12 v and ground, intermediate tap tone to 6 v, or will IC501 {and} feet and external circuit disconnect, then adjustable resistance to tap voltage of commissioning in the middle. The image back to normal. Adjustable adjustable resistance contrast have corresponding change, when that IC501 without exception, fault in the peripheral circuit. Fnqservice manual download site
 Fnqservice manual download site
Along the IC501 {and} foot branch to the CPU (IC1101) inspection, found that the CPU {12} feet voltage is low. Check the foot of the peripheral components CP1106, C1111, ZD1107, found stabilivolt ZD1107 reverse resistance value is only about 3 k Ω. After replacing ZD1107 IC1101 {12} feet between 0 ~ 10 v voltage adjustable, troubleshooting.Fnqservice manual download site