The part color TV channel audio noise big, individual channel without sound and picture quality is poorer, even after manual fine-tuning the audio, image can be restored to normal; To automatically search, lock, all normal, but poor sound channel audio is still poor, conversion channel instantaneous sound normal xCKservice manual download site
 xCKservice manual download site
Poor sound channel can be normal after manual fine tuning, shows that the fault is not in the audio channel, but high frequency tuning is not accurate. The machine with high frequency tuning voltage of BT and AFT, monitoring of high frequency voltage corresponding pin head, found in the transformation channel instantaneous voltage of the AFT of 4.4 V, then fell to about 0.8 V at a faster pace, sound variation, then the voltage of the BT remains the same. Therefore, judge the fault in the AFT circuit. xCKservice manual download site
In the voltage synthesis type remote control color TV tuner, there are generally two kinds of AFT control mode, a kind of according to the CPU for putting AFT circuit output voltage change, adjust the output voltage at the BT, to guarantee the accuracy of the high-frequency tuner tuner in receiving channel. Such forms of high frequency head does not need to set the AFT circuit terminals, the AFT and optional functions undertaken by BT terminal machines, into the AFT circuit output voltage corresponding port only sent to the CPU. Another CPU for AFT delivered into the circuit voltage only for tuning lock machine, high frequency head AFT control required for setting up a special terminal, directly by putting AFT circuit output voltage control. In this kind of control mode, in order to avoid in the process of searching the AFT voltage changes affect the accuracy of the lock, need of setting up AFT switch. AFT switch when searching, high-frequency head AFT terminal plus fixed voltage; In normal watch, AFT switches, high-frequency head AFT terminal voltage controlled Yu Zhongfang AFT voltage. The native AFT control mode by the latter.

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