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AUDIO PROBLEMS
Problem:
Check:
1.First, make sure you have an audio signal applied to both left and
right inputs then try pressing the headphone level up button for a
second or two. If you still don't hear any audio go to step 2.
2.Use the headphone test jig to test Pin2 on U11 and U12. If you
hear audio signals go to step 3. Otherwise go to step 4.
3. Use the headphone test jig to test Pin 5 on U11 and U12. If you
hear audio signals check all components and connections between
these pins and J20. Also make sure the ground connection on J20
is soldered properly. Otherwise go to step 4.
4. Measure the voltage on pin 1 of U11 and U12. [Reading =
+5VDC +/- 0.2VDC] If the correct voltage is present check all
connections and components connected to U11 and U12. If you still
can't find the problem go to step 5.
5. Measure the voltage on pin 4 of U11 and U12. This reading will
be between 0 and +5VDC depending on the setting of digital
potentiometer U10. Press the up or down headphone level buttons
and observe if the reading increases and decreases. If it does NOT
change check all connections on U10 for opens or shorts and also
measure the voltage on pins 1 and 8 on U10. If you do not measure
+5VDC trace and check the 5VDC circuit back to the 5 volt regulator
VR2.
Problem:
Check:
1.Check to make sure the jumpers on headers H1 and H2 are
installed properly between either pins 1 and 2 or pins 2 and 3
depending on the desired configuration. If not correctly installed,
install them and recheck the outputs. Otherwise go to step 2.
2. With good audio in the headphones only the line output buffer
circuit can be at fault. Measure the voltage on U10 pins 8, 9, 10,
11,12, and 14. [READING = +5VDC +/- 0.02VDC] If not correct
check the placement and connections of R4 and R30. If correct go
to step 3.
3. Use the headphone test jig to check for signal on pins 10 and 12
of U1. If signal is present go to step 4. Otherwise check for opens
on the signal path between pin 2 on H1 and H2 and pins 10 and 12
on U1. Also check that C13 and C14 are installed correctly.
4. Use the headphone test jig to check for signal on pins 8 and 14 of
U1. If no signal is present check the signal path between these pins
No audio from headphones only
No audio from only the line output jacks J1 and J8
UAM4SYS • 30
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