Home appliances common sense
Escape TV troubleshooting analysisEscape TV stands, there are two phenomena: all frequencies are run only appeared to escape a band of Taiwan. Formation mechanism of failure there are two main types, do one of the following introduction.
a high frequency head VT end voltage not stability by caused
for high frequency head tuning voltage not stability and caused of escape Taiwan fault is most common of reasons, its fault reasons has:
1, and 33v tuning electric not stable;
2, and tuning Board Shang channel preselection switch, and co-ordination potentiometer contact bad or co-ordination Board itself bad; (non-remote control TV);
3, and CPU bad (containing storage integrated block);
4, and Interface circuits (VT outputs to the tuner VT terminal) elements are unstable leakage.
5 unstable leakage, high frequency tuned circuits in the head.
repair of the fault is: first disconnect the tuner VT terminal connections with the external circuit, and into the micro-ampere-meter, if current in 5 UA and unstable, it is related to the tuner itself. Otherwise, is the failure of 1-4.
AFT circuit/> two AFT circuit work principle is generated by the class in an oscillation frequency error voltage, tuner AFT terminal access, to control the frequency of this magnitude. So when the circuit fails, can also lead to escape. Its features are:
1, high frequency head AFT circuit: AFT circuit within the tuner, tuner external AFT circuit (including CPU)
2, AFT circuit: AFT shift in phase-frequency transformers, image detection in transformers detuned; put the AFT the chip circuit failure.
is AFT circuit failure, repair is: high frequency meter head AFT Terminal voltage if normal but not stable (normal voltage 6.5V) tuner AFT Terminal is disconnected, then again, if stable, then the fault in the tuner circuit AFT. While in tuner external circuits, you can turn off AFT switches and AFT measurement voltage, such as stability is put the problems of the chip, on the contrary, is the AFC branch voltage circuit or CPU failure.