Service manual

MFC-8420/8820D/8820DN, DCP-8020/8025D/8025DN
SERVICE MANUAL
6-33
F-5
Speaker is silent during on-hook dialing.
Possible cause Step Check Result Remedy
Connection
between main
PCB and
speaker
1
Main PCB and speaker are
properly connected.
No Fix the connection properly.
Speaker 2
Replacement of speaker
solves the problem.
Yes Replace the speaker with a
normal part.
Connection
between main
PCB and NCU
PCB
3
Main PCB and NCU PCB are
properly connected.
No Fix the connection properly.
Harness
between main
PCB and NCU
PCB
4
Harness wire is damaged. Yes Replace the harness with a
normal part.
Connection
between main
PCB, relay PCB,
and control
panel PCB
5
Main PCB, relay PCB, and
control panel PCB are
properly connected.
No Fix the connection properly.
Harness
between main
PCB, relay PCB,
and control
panel PCB
6
Harness wire is damaged. Yes Replace the harness with a
normal part.
NCU PCB 7
Replacement of NCU PCB
solves the problem.
Yes Replace the NCU PCB with
a normal part.
Relay PCB 8
Replacement of relay PCB
solves the problem.
Yes Replace the relay PCB with a
normal part.
Main PCB 9
Replacement of main PCB
solves the problem.
Yes Replace the main PCB with
a normal part.
F-6
Dialing function does not switch between "tone" and "pulse".
Possible cause Step Check Result Remedy
Connection
between main
PCB and NCU
PCB
1
Main PCB and NCU PCB are
properly connected.
No Fix the connection properly.
Harness
between main
PCB and NCU
PCB
2
Harness wire is damaged. Yes Replace the harness with a
normal part.
NCU PCB 3
Replacement of NCU PCB
solves the problem.
Yes Replace the NCU PCB with
a normal part.
Main PCB 4
Replacement of main PCB
solves the problem.
Yes Replace the main PCB with
a normal part.