Troubleshooting - Casio Realistic Concertmate 500 Service Manual

TROUBLESHOOTING
Trouble Checkpoints and
Possible
Cause
Does not
work
at
all
(Pilot
lamp
does not
light)
•
Check
the voltages
VA
(+SV),
VE
(+3 .35V),
VC
(+5V) and
VD
(+5V).
•
Check
the
reset
and
APO
signals.
• Faulty
parts:
Transistors
Tt
Power
switch,
or
CPU
(LSI
1).
Does not
work
at all
(Pilot
lamp
lights)
•
Check
the voltages
VH
(+7.5V),
VC
(+5V) and
VD
(+5V).
•
Check
the clock pulse and key
common
signals.
• Faulty
parts: Transistors
T5
T8.
Ceramic Trimmer
VCT84K.or
ROM
(LSI
4).
1
'1
Preset
tone does not
1
sound on
PLAY
mode
•
Check
the voltage
VH
(+7.5V).
•
Check
the analog
signal at
base
of transistor
T1
1
or
Power
amp.
(IC1).
•
Faulty
parts:
Transistors
T7
T9, Til,
CPU
(LSI
Dor
Power
Amp.
(ICl).
Chord
or Bass
tone
does not sound on
C)HORD mode
•
Check
the analog
signal at
collector of transistor
T18
or
T23.
•
Check
the analog
signal
at
source of
FET
TIO.
• Faulty
parts:
Transistors
T18
"*'T23,
TIO,
or
Analog
Switch
(IC2).
Melody
or
Obbligato
tone does not
sound
on
SOLO
1
or
SOLO
2
mode
•
Check
the analog
signal at collector
of
transistor
T13
or
T17.
and
at
emitter
of transistor
Til.
• Faulty
parts:
Transistors
T12 T17
or T1
1.
Memory/Oemo
play
does not
perform
• Faulty pans;
RAM
1
(LSI
4),
ROM
(LSI
2).
CPU
(LSI
Dor
Chip
Selector (IC3).
Sampling
impossible
•
Check
the analog
signal at collector
of
transistor
T25
at
sampling
time.
•
Check
the
vol
tage (2.5
V
)
of pin
1
00
of the
CPU
{
LSI
1 ).
• Faulty
parts: Transistors
T24, T25.
CPU
(LSI
1
).
RAM
1
(LSI
4)
or
Chip
Selector (IC3).
Distorted
sound •
Faulty
parts:
Transistors
T1
2 T20, T9, or
Power
Amp.
(ICl).
A
certain
key
or switch
does not respond
•
Check
the contacts of
PC
joirter
or contact rubber.
•
Clean
the contacts
on
the
keys and
the switches.
Percussions
do
not
sound
•
Chedc
the analog
signal at
pin
97
of the
CPU.
•
Check the
poor
soldering
on
pin
97 of the
CPU.
•
Faulty
parts:
CPU
(LSI
1).
Reference
Waveform
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