Example 14 Not read DVD
Analysis and troubleshooting: Step 1: check XS301 socket and flat cable and no abnormality is
found (you may observe directly, and you need to insert it again when you find that flat cable is loose).
Step 2: change loader and trouble is removed.
Conclusion: in actual servicing, when you meet the trouble such as no disc reading, it is always
difficult to judge which element has trouble, so you may try changing loader to judge where the trouble is
in.
Example 15 No disc reading
Analysis and troubleshooting: shown in the figure 3.3.1.5; Step 1: check each flat cable and no
abnormality is found.
Step 2: after changing loader, disc reading is still unavailable.
Step 3: observe laser head and find no focus acts (after opening door), other acts are normal, so it
is preliminarily judged that servo circuit has trouble.
Step 4: check and find that power supply on pin 8, 9 of U301 (D5954) is normal, and that on pin 21
is also normal, check reference voltage on pin 4 of U301 and it is 1.4V, which is also normal.
Step 5: check U302, R211 and C213 and no abnormality is found.
Step 6: after changing U301 (D5954), trouble is removed.
Conclusion: in actual servicing, it is difficult to judge whether an IC has trouble or not; sometimes
you may try considering changing IC and check whether trouble is removed. If there is digital
oscillograph, firstly check the end close to MT1389 of R211, if there is waveform (waveform diagram in
section 4) within a small period (about 5 seconds) after disc in, the possibility that MT1389 has trouble is
small, and D5954 may probably have trouble.
Example 16 No disc reading
Analysis and troubleshooting: shown in the figure 3.3.1.5; Step 1: check each flat cable and no
abnormality is found.
Step 2: after changing loader, still no disc reading, and trouble is still not removed.
Step 3: observe laser head and find that focus, feed and main axis have no acts, even that laser
head does not emit laser light.
Step 4: check power supply and clock circuit of MT1389 and some abnormalities are found.
Step 5: use oscillograph to test the end close to MT1389 of R208, R209, R210, R211 (test within a
small period after disc in), and find no obvious waveform output, so we preliminarily judge that MT1389
has trouble, after changing MT1389, trouble is removed.
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