Casio SK 8A - 15. TROUBLESHOOTING

15. TROUBLESHOOTING
TROUBLE
FAULTY BLOCK
CHECKPOINT
No Power
Power Circuit
Checkpoints' voltages in accordance
with the schematic diagram
Power Switch Switch contacts and switch spring
tension
Reset Circuit Waveform (T)
Power ON Detector
Waveform (2)
CPU (MSM6293)
Pulse Generator
Waveform (3)
ROM (pPD23C256EAC)
No sound at all
Power Circuit Voltages VA, VX
Reset Circuit
Waveform (T)
Pulse Generator
Waveform (3)
CPU (MSM6293)
ROM (/UPD23C256EAC)
Mixing Amp.
Emitter of transistor Til
Power Amp. (LA4138)
Pin 2
Speaker
Speaker terminal (red wire)
No melody, chord, bass, and
CA91A02
obbligato (percussion sounds)
Filter
Emitters of T14 and T15
CPU (MSM6293)
ROM (pPD23C256EAC)
No chord, bass, and obbligato
CA91A02
Gain Controller
Pin 11 of TC4066
CPU (pPD23C256EAC)
ROM (pPD23C256EAC)
No percussions
Percussion Generator (MSM6294)
Pin 19
Clock Pulse Generator
Waveform (4)
Percussion Filter
Emitter of T12
CPU (MSM6293)
ROM (pPD23C256EAC)
ROM packs cannot be palyed
ROM Pack
RAM (pPD43256C)
CPU (MSM6293)
ROM <pPD23C256EAC)
Certain keys or switches do
Dirty contacts
not respond
Broken or poor-soldered PC Joiner
Sampling impossible
Microphone
Sampling Circuit
Collectors of T28 and T29
CPU (MSM6293)
RAM (pPD43256C)
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