Brother MFC8440D Service Manual page 236

7/13/2019
Speaker is silent during on-hook dialing.
F-5
Possible cause
Connection
between main
PCB and
speaker
Speaker
Connection
between main
PCB and NCU
PCB
Harness
between main
PCB and NCU
PCB
Connection
between main
PCB, relay PCB,
and control
panel PCB
Harness
between main
PCB, relay PCB,
and control
panel PCB
NCU PCB
Relay PCB
Main PCB
Dialing function does not switch between "tone" and "pulse".
F-6
Possible cause
Connection
between main
PCB and NCU
PCB
Harness
between main
PCB and NCU
PCB
NCU PCB
Main PCB
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Step Check
1 Main PCB and speaker are
properly connected.
Replacement of speaker
2
solves the problem.
Main PCB and NCU PCB are
3
properly connected.
Harness wire is damaged.
4
Main PCB, relay PCB, and
5
control panel PCB are
properly connected.
Harness wire is damaged.
6
Replacement of NCU PCB
7
solves the problem.
Replacement of relay PCB
8
solves the problem.
Replacement of main PCB
9
solves the problem.
Step Check
1 Main PCB and NCU PCB are
properly connected.
Harness wire is damaged.
2
Replacement of NCU PCB
3
solves the problem.
Replacement of main PCB
4
solves the problem.
Brother 8840D Service Manual
MFC-8440/8840D/8840DN, DCP-8040/8045D/8045DN
Result
No Fix the connection properly.
Yes Replace the speaker with a
normal part.
No Fix the connection properly.
Yes Replace the harness with a
normal part.
No Fix the connection properly.
Yes Replace the harness with a
normal part.
Yes Replace the NCU PCB with
a normal part.
Yes Replace the relay PCB with a
normal part.
Yes Replace the main PCB with
a normal part.
Result
No Fix the connection properly.
Yes Replace the harness with a
normal part.
Yes Replace the NCU PCB with
a normal part.
Yes Replace the main PCB with
a normal part.
6-33
SERVICE MANUAL
Remedy
Remedy
236/361