PAMS
Technical Documentation
NSB–1/3
Troubleshooting Instructions
Page 21
Original 06/98
Audio failure (1)
Uplink (microphone) and downlink (earphone) are broken
Voltage at pin 107 of MAD2 (D200)
is 2.8 V (without external audio de-
vices) HOOKDET
NO
YES
Check
R130,R155,
R300,C300
Voltage at pin 108 of MAD2 (D200)
is 2.8 V (without external audio de-
vices) HEADDET
NO
Check
R154,R301,,R302,
R300,R332,
C306,C308
YES
Frequency at pin 138 of MAD2 (D200)
is 1 MHz, square wave 2.8 Vpp
NO
Check
N300 (Cobba)
Frequency at pin 139 of MAD2 (D200)
is 8 kHz, square wave pulses 2.8 Vpp
YES
NO
Check
N300 (Cobba)
YES
Uplink (microphone) is broken
Voltage at pin 6 of X131 is 1.8V
Voltage at pin 7 of X131 is 0.3V
NO
YES
during a call
YES
DC voltage at pins 59 and 60 of
N300 is 1.4 V during a call
NO
Check
N300 (Cobba)
YES
Analog audio signal (few millivolts) at pins 59 and 60
of N300 during a call
NO
Check
C336, C335 and PCB
routings
YES
Check
N300 (Cobba)
Digital PCM data at pin 137 of MAD2 (D200)
during a call
NO
Check
microphone
Check X131 and micbias
components: V300,R335...
ok