14
KX-TS880MXB/KX-TS880MXW
8.3.
Tone Dialing Problems
8.4.
No Ringing Sound When Ring Signal is Input
Does the DTMF signal
appear at base of Q422?
Does the DTMF signal
appear at Pin91 of IC801?
Can the DTMF sound
be monitored ?
YES
YES
NO
Check Q422, Q107.
Check C485, R487, R490,
C415, L411, L409 and
Q403.
Check R481, R485, R486,
R488, C483, R483, L421
and R430.
NO
Check IC801 and X1.
NO
YES
Is the voltage
across Pin 8 and Pin 2 of
Check the telephone line.
Check C1, R1, R2, D1,
and LED1.
Does a sine wave of approximately 60V
or more appear across Tip and Ring?
YES
NO
YES
Call the unit from another telephone.
Does the tone ringer output signal
appear across Pin 5 and Pin 2 of IC1?
NO
NO
Check IC1, R3, R4, C3 and
C4.
YES
Check the Ringer SW2, PC1, C5 and T1
IC1 30 Vp-p?
