This failure is decoding circuit automatically decolorization (ACK) circuit failure caused by. When decoding circuit is normal, decolorization detection end detection voltage of 26 feet: when receiving the color signal often 10 v; Receive weak color signals or black since 9 v, namely the decolorization circuit starts, decolorization voltage drop 1 v. This is the key to determine whether decoloring circuit normal test points. SWaservice manual download site
(1) receiving color bar signal generator signal, measuring IC501.26 foot voltage of 10.5 V. When converted to black since the signal color bar machine, the voltage is still more than 10 v 26 feet. SWaservice manual download site
(2) check the 36 feet external components R527, C504 are good, so the suspect IC501 bad inside. When further examination is 26 feet resistance, found on the 12 v power supply only about 100 k Ω, and 26 feet off the circuit board, the source resistance is very large. So prove 26 feet circuit for the power cable leakage, thus make the chrominance channels open all the time, cause not decolorization of failure. SWaservice manual download site
(3) saw blade cleaning between 26 feet and power cable, and use alcohol to clean, dry after troubleshooting.SWaservice manual download site