Section Three Troubleshooting Cases
3.3.1 Troubleshooting Cases
Example 1 Symptom Power not on
Description Plug unit, power standby indication light is not on, power on is not available.
Analysis and troubleshooting: detect power board, 5V and 3.3V voltages are all normal. Detect
power supply of decode board MT1389 chip are 3.3V and 1.8V, which are normal. Use oscillograph to
check 27MHZ crystal oscillator provided to MT1389 chip oscillator frequency is abnormal, which is
smaller. Crystal oscillator is doubted to be bad, replace it and trouble is removed.
Example 2 Symptom: DVD disc reading is unavailable
Description Focus, feed, main axis and track of pick up are all normal except that light emitting is
unavailable.
Analysis and troubleshooting: power off, use multimeter to check triode 1Q, which is not damaged.
Communication of LD02 and MT1389 is normal. Power on and check working condition of Q1, it is found
that emitter of Q1 has no 3.3V power. Check the play and 3.3V power is normal. From the circuit diagram,
it is found that 3.3V is used for Q1 emitter through R9. It is doubted that it may be caused by Q1
metamorphose. Use resistance 2K of multimeter to check and found that resistance value is
infinitely-great. Replace it, emitter of Q1 is 3.3V, which is normal. Pick-up emites DVD laser normally
and trouble is removed.
Example 3 Symptom Front channel of power amplifier has no sound output
Description mix sound of player AV board outputs normally. While front channel of power amplifier
has no sound output.
Analysis and troubleshooting: use multimeter to test pin 1 of power board XS101, which is +28V
normal. Then check pin 1 of decode power amplifier board CON4, which is also +28V and it is normal. It
can be confirmed that IC supplies power normally. Use oscillograph to check whether vertical type
screened inductance L513 L514 have wave. It is found that there is no wave output, Thus it confirmed
that power amplifier N508 is uneffective, replace it and trouble is removed.
Example 4 Symptom: small wave
Description: waves outputted form left and right mix audio terminal are all small
Analysis and troubleshooting: For the trouble that waves outputted form left and right mix audio
terminal are small, it is probably caused by common used elements by two channels are bad. Firstly
check whether audio terminal is bad connecting or rosin joint. Exclude the above factors, then check IC
power supply of location number N503, N504 on power amplifier are all +5V power supply of N509 is
3.3V and it is also normal. Check AD transferring voltage ADACVDD of audio signal, which is 2.4V and it
is a litter bit small. And the normal voltage is 3.3V. It is found that resistance of two sides of L13 is
infinitely great, thus it is confirmed that L13 is metamorphosed, replace it and trouble is removed.
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