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Buttons on remote control and find that pin 1 voltage of CN105 has no change. Under normal conditions,
when pressing remote control, voltage changes from +4.98 to 3V plus several, which means remote
control information has been received, so trouble should be in remote control receiver. After changing,
trouble disappears.
[ Example 8 ] symptom: in AV input mode, video output end of SCART terminal has no vide signal output.
Trouble description: select signal source in AV state, switch on DVD Player to play demonstration
disc and screen has no picture. SCART is used to output signal to external TV and there is still no picture
display, but sound output is normal.
Analysis and troubleshooting: according to trouble symptom, we judge that trouble lies in video
output circuit. If video signals of LCD of this player are normal, it means external input circuit is normal.
After being processed by MST718, externally inputted video signals switch to digital video signals to
output to display screen; other signals output from pin 34 as analog signals to SCART terminal through
amplifying circuit to act as video output signals.
Use oscillograph to observe
Ce108, there is no signal output, but the end that connects R42 and Q1 has signal output. Observe R2
carefully and the surface has leakage. After power off, use iron to heat R2 and then cut off. Change R2
with the same specification, trouble is removed.
shown in the figure 3.3.1.2,
figure 3.3.1.2 video out circuit diagram
[ Example 9 ] Symptom: speaker has no sound
Description: in any external input mode, there is no sound output.
Analysis and troubleshooting: set signal source in “AV" state, turn on DVD Player demonstration
disc and use oscillograph to test left/right speaker and find that there is no signal waveform output, so
we confirm trouble should appear in precious stage circuit. test pin 8, 17 input pin of U112(TDA7226)
and find that there is waveform input, but pin 9, 20 have no waveform output. Then test power supply
Loop and +12V voltage changes to +10.8V after voltage drops, which is normal. Observe whether pin