Troubleshooting - Casio SK 8A Service Manual & Parts List

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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19
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