14
Model No: CT-21FDS1
Version 1.0
2. Two-None (no picture, no sound)
The failure shows that the set does not display the picture but it has noise wave or blue background or OSD on the screen. This means that the circuits of power supply, horizontal scanning, vertical scanning and video amplification
are normal and they are not considered in the repairing. The failures are mainly in the small signal processing circuits.
Before checking these circuits, a kind of practical test method is introduced. It is called “Signal-input way ”. The detail is described as follow: We can use the resistance function of an analog multimeter, connect the red pole (negative
in ohm scope) on the circuit board ground, then touch softly the test point with another pole (black pole) in ohm scope meanwhile observe the reactivity on the output device.
Note: In the TV test, we mainly observe the noise wave on the CRT and listen to the noise voice liking as “Ka…..Ka” from the loudspeakers.
a. No
picture
Out of the “ 0-33V ” range
0V
NO
No picture
Check the “ +9V ” voltage on A101
Check RF signal input and adaptor
CheckN902, TUN101
Check N101,R968,R969,
N201,A101
Check the “ VT ” voltage when auto searching
Check R102, C102, TUN101
The voltage between VL and BH vary from
0V to 9V or not when auto searching
Check R553,N904,C973
The voltage on the C992
Check the voltage on the C992
Check ,V975,D901, R973, R975
,R975,R990,C971,C972,C991
Check if A101 has input signal
0V
YES
In the “ 0-33V ” range
5V
33V
33V
0-33V
