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RM-356
BB Troubleshooting and Manual Tuning Guide
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 2kHz.
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. 1kHz
sine wave from 5cm distance.
Required equipment
The following equipment is needed for the tests:
• Oscilloscope
• Function generator (sine waveform)
• Current probe (Internal handsfree PWM 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 microphone to Internal earpiece
• External microphone to Internal handsfree speaker
• HP microphone to External earpiece
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.
Issue 1
COMPANY CONFIDENTIAL
Page 3 –59
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