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
Waveform
@
Waveforms
@
Waveform(^
Waveform
@
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