Example 11 Component color distortion
Analysis and troubleshooting: Step 1: check MT1389 clock, 26.999MHZ, VPP=1.72V, normal
(27KHZ when in normal conditions).
Step 2: check MT1389 power supply and it is normal.
Step 3: use oscillograph to test the 3 component signals of pin 6 (Y4), pin 7 (Y5) and pin 8 (Y6) of
XP206 on AV board and they all have output, but when using multimeter to test DC voltage of the 3
signals, we find that Y5 has +4.7V, in normal conditions, this voltage should be two several tenths of a
volt and one volt plus a little at most.
Known from the circuit, only when damping diode has trouble, it has the most possibility to make
this voltage increase; when using multimeter to test diode, we find that VD100 has been stricken
through, after changing it, trouble is removed.
Note: as for colour distortion problem, if problem of capacity has electric leakage, inductor has
open circuit, damping diode is stricken through and or short circuit is found, please firstly consider
changing Mt1389.
Example 12 Component video has no output
Analysis and troubleshooting: use oscillograph to test VIDEOY1, VIDEOU, VIDEOV (VD103,
VD101, VD111 anode), VIDEO Y1 has no output; VIDEOU and VIDEOV have output. Test pin 6 of
XP206 and pin 6 of XS206 on decode board, there is no waveform output basically. Disconnect the flat
cable between XP206 and XS206, waveform of pin 6 of XS206 resumes normal, so we estimate that
trouble lies in filtering circuit on AV board. Check R108, C112, C114, VD102, VD103 and find that VD102
is stricken through, after changing VD102, component video output is normal.
Example 13 Power not on
Analysis and troubleshooting: Step 1: check power supply of power board and all output all normal.
Step 2: check the output of 1.8V voltage regulator and it is +1.9V, which is normal.
Step 3: check clock frequency of two ends of X201 in clock circuit and it is normal.
Step 4: check the output of pin 6 of reset circuit U205 (HCU04) and it is +3.4V, which is normal.
Step 5: reset bu force (use a lead to make U205 (HCU04) grounding for about one second) and find
that power may be on, and the player may work normally; power of again after power off, and find that
power may be on, but after power on and off repeatedly for several times, power will be off again, after
reset by force, it may power on freely.
Step 6: after changing U205 (HCU04) and power on repeatedly (above ten times), there is no
abnormality that power not on, so trouble is removed.
Conclusion: power also may be on when reset circuit has trouble, but it is not on sometimes, which
may be caused by random trouble, now you need to test repeatedly to confirm whether reset circuit has
trouble.
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