JCM GOLD GP-965 Service Manual - page 11
GP-965 service
manual
11
4
REPAIR ON THE UNIT LEVEL
4.1 Main Circuit Board Unit
PHENO-
MENON
DETAIL
CAUSE
CHECK
REPAIR-
METHOD
Abnormal +5V power
supply
Faulty zener diode
ZD6,diodes D1,D3,
and regulator
U2(LM2575T-5.0)
Check the +5V supply
voltage in pin4 of U2
Replace ZD6, D1,
D3 and/or U2
Abnormal oscillator
circuit in CPU
Faulty oscillator X1
Check if the oscillator is
oscillating properly
Replace X1
Abnormal section of
program ROM
Faulty U15(CPU) and
U5
Check the pin39 output of
the CPU and pin10 output
of the U5
Replace the U15
and/or U5
Abnormal RAM
selection
Faulty U8, U12 and/or
the U15(CPU)
Check the pin1 output of
the CPU, pin3 and pin11
of U8, and pin3 of U12
Replace U8, U12
and/or the CPU
Abnormal drive of DC
motor
Faulty TR3, U10 and
CPU
Check the pin25 output of
the CPU and pin9 output of
U10. Check if TR3 is
normal.
Replace the CPU,
U10 and/or TR3
Abnormal BOF sensor
operation
Faulty U15(CPU)
Check the pin37 output of
the CPU
Replace the CPU
Abnormal TOF sensor
operation
Faulty U15(CPU)
Check the pin36 output of
the CPU
Replace the CPU
Abnormal ROM
Abnormal U7
Replace U7
Abnormal RAM
Abnormal U11
Replace U11
The printer
doesn’t
operate at all
Abnormal CPU
Faulty U15(CPU)
Check pin42(ALE signal)
of the CPU
Replace the CPU
Faulty
carriage
operation
The carriage doesn’t
work at all
Abnormal +24V supply
voltage
Check +24V voltage in
pin1, 2, 3, 4 of CN5
Check power
supply
No printing is
performed
Faulty charge pulse
circuit
Check the collector TR3
output, pin25 output of U15
and pin9 output of U10
Replace U10, U15
and/or TR3
Abnormal
printing (by
the self test)
Certain dots are never
printed
Faulty transistor TR5,
U8 and/or U14
Check the output of TR5,
pin8 output of U8, pin13
output of U14
Replace the TR5,
U8 and/or U14
Abnormal
release
operation
No paper release is
performed
Faulty CPU, TR8
and/or D27
Check pin23 output of CPU
and TR8. Check if D27 is
normal
Replace the CPU,
TR8 and/or D27
Paper feeding
is abnormal
No paper feeding is
performed
Faulty CPU, TR6, TR7,
U13 and D25
Check pin24, 44, 45, 46,
47 output of the CPU, and
TR6 and TR7. Check if the
D25 is normal
Replace the CPU,
TR6, TR7, D25
and/or U13
The panel
switches
don’t operate
properly
Faulty U16
Check pin7 and pin9 of
U16
Replace U16