Troubleshooting - Casio CTK-500 Service Manual

Nature of Trouble
No power
No sound at all
Distorted sound
All or certain keys do
not function
A certain key does not
function

TROUBLESHOOTING

Faulty Block
Power Jack (J1)
Power IC (IC1: CA5668)
Reset IC (IC4: S8053ANO)
Power Switch
Main Clock Generator (X1)
CPU (LSI1: MSM6626-01)
Power Amp. (IC2: LA4127)
CPU (LSI1: MSM6626-01)
ROM (LSI2: MN232000CUQ)
ROM (LSI2: MN232000CUQ)
CPU (LSI1: MSM6626-01)
Power Amp. (IC2: LA4127)
Power IC (IC1: CA5668)
CPU (LSI1: MSM6626-01)
Key Matrix
Key Matrix
— 11 —
Checkpoint
Jack contact.
Pin 8 should have +5 V.
Pin 6 should provide + 5V when pin 10
receives + 5 V.
Pin 1 should provide a low level pulse when
an AC adapter is connected.
Pin 22 of CPU should receive a trigger
pulse when turning on the switch.
Check oscillation at pin 34 of CPU.
Pin 12 should provide +5 V when turning on
the power switch.
Check output waveforms of pins 9 and 12.
Check output waveforms of pins 25 and 26.
Check CE signal of pin 10, and OE signal
of pin 12.
Check address/data bus.
Check output waveforms of pins 25 and 26.
Check output waveforms of pins 9 and 12.
Check voltages of pins 2 (+9 V) and 6
(+5 V).
Check KO signals of pins 1 to 4, and 74 to
80.
Open circuit on KO or KI line.
Dust on the contact.