[ Example 8 ] Symptom: machien down when power on.
Description: after power on, machine down before entering menu operation.
Analysis and troubleshooting: when power on, machine down before entering main menu. Press
PLAY button to power on, when screen appears BBK picture justly, image of the player halts and button
has no function. Firstly test power supply 3.3V, 3.8V and it normal. Then test crystal oscillator oscillation
frequency and it is normal, so we judge that data has abnormality. Because machine down, data cannot
be tested normally. Change main chip and trouble still exists. After changing Flash U4, trouble is
Removed.
[ Example 9 ] Symptom: machine down when tuning.
Description: machine is normal when playing Mp3, Mp4. Machine down when entering tuning state.
Analysis and troubleshooting: firstly check tuning IC power supply 3.3V, and SCL, SDA are normal.
Test whether 32.768 crystal oscillator oscillates normally and whether it has false welding. This crystal
oscillator has direction when changing it, so it cannot be stuck reversely, otherwise machine down will
happen. Test crystal oscillator and we find it has false welding. After welding again, trouble is removed.
Example 10 ] Symptom: computer cannot be connected.
Description: after connecting with computer, no display and disk cannot be found.
Analysis and troubleshooting: firstly confirm whether charge is available and it is normal after
power on. Use diode level of multimeter to test the resistance value to ground of D+, D- data signals in
USB terminal position and it should be close to several hundred ohm. Then test between D+ and D- and it
should not have short-circuit. Test DP and DM and they are normal. Test power supply 3.3V, 1.8V and it
is normal. Crystal oscillator oscillates normally. Change chip Rk2608, upgrade software again, connect
with computer and trouble is removed.
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