PAMS
Technical Documentation
NSC/W–1/3
Disassembly & Troubleshooting Instructions
Page 17
Original 11/99
Audio failure
Uplink (microphone) and downlink (speaker) are broken
Voltage at pin 78 of MAD1 (D202)
is 2.8 V (without external audio de-
vices) HOOK.
NO
YES
Check
R260, R270
Voltage at pin 77 of MAD1 (D202)
is 2.8 V (without external audio de-
vices) HEADSETINT
NO
Check
R268, R265, R260
YES
Frequency at pin 5 of MAD1 (D202)
is 1 MHz, square wave 2.8 Vpp
NO
Check
N250 (Cobba)
Frequency at pin 6 of MAD1 (D202)
is 8 kHz, square wave pulses 2.8 Vpp
YES
NO
Check
N250 (Cobba)
Uplink (microphone) is broken
Voltage at pin 6 of X100 is 1.8 V
Voltage at pin 7 of X100 is 0.3 V
NO
YES
Check
microphone, X100 and micbias
components V250...
If OK, check that VR1_sw is 2.8 V
during a call
during a call
YES
DC voltage at pins 38 and 39 of
N250 is 1.4 V during a call
NO
Check
N250 (Cobba)
YES
Analog audio signal (few millivolts) at pins 38 and 39
of N250 during a call
NO
Check
C256, c285 and PCB
routings
YES
Check
N250 (Cobba)
Digital PCM data at pin 12 of MAD1 (D202)
during a call
NO
YES