Audio troubleshooting
Audio troubleshooting test instructions
Single-ended external earpiece and differential internal earpiece outputs can be measured either with a
single-ended or a differential probe.
When measuring with a single-ended probe each output is measured against the ground.
Internal handsfree output is measured using a current probe, if a special low-pass filter designed for
measuring a digital amplifier is not available. Note also that when using a current probe, the input signal
frequency must be set to 2 kHz.
The input signal for each loop test can be either single-ended or differential. Exception to this is a digital
microphone which needs input signal from an external sound source (laptop speaker) to playback, eg. 1 kHz
sine wave from 5 cm distance.
Required equipment
The following equipment is needed for the tests:
•
Oscilloscope
•
Function generator (sine waveform)
•
Current probe (Internal handsfree DPMA output measurement)
•
Phoenix service software
•
Battery voltage 3.7V
•
Sound source (laptop speaker or B&K type 4231 calibrator)
Test procedure
Audio can be tested using the Phoenix audio routings option. Three different audio loop paths can be
activated:
•
External headset mic to earpiece
•
External headset mic to IHF mono
•
Internal digital microphone to headset
Each audio loop sets routing from the specified input to the specified output enabling a quick in-out test.
Loop path gains are fixed and they cannot be changed using Phoenix. Correct pins and signals for each test
are presented in the following table.
Phoenix audio loop tests and test results
The results presented in the table apply when no accessory is connected and battery voltage is set to 3.7V.
Earpiece, internal microphone and speaker are in place during measurement. Applying a headset accessory
during measurement causes a significant drop in measured quantities.
The gain values presented in the table apply for a differential output vs. single-ended/differential input.
Loop test
Input
terminal
Output
terminal
Path gain
[dB]
(fixed)
Input
voltage
[mVp-p]
Output DC
level [V]
Output
voltage
[mVp-p]
External
headset
mic to
earpiece
HS_MIC &
GND
EAR 1 &
GND
0
300
1.35
300
EAR 0 &
GND
RX-51
BB Troubleshooting
Issue 1
COMPANY CONFIDENTIAL
Page 3 –35
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