CASIO CTK750
Service Manual

Electrical
Current Drain with 12V DC: No Sound Output Maximum Volume with white keys D2 to D3 pressed in Synth-Bass-2 tone and in Latin Fusion rhythm at initial setup tempo Volume; maximum, Touch: maximum Line Output Level (Vrms with 47 K� load each cannel): with key D4 pressed in FSynth-Bass-2 tone on L-ch with key G4 pressed in FSynth-Bass-2 tone on R-ch Phone Output Level (Vrms with 8 � load each channel): with key D4 pressed in FSynth-Bass-2 tone on L-ch with key G4 pressed in FSynth-Bass-2 tone on R-ch Speaker Input Level: with key D4 pressed in FSynth-Bass-2 tone on L-ch with key G4 pressed in FSynth-Bass-2 tone on R-ch Minimum Operating Voltage:
I S

390 mA ± 20% 1700 mA ± 20%

Note: To increase productivity ,the DSP HG51A115A01FD is sticked on the main PCB with a double-side adhesive tape, then its leads are soldered. Remove the DSP according to the following procedures. 1. Prepare isopropyl alcohol and a flat IC desoldering machine (Spot Heater HS-600). 2. Apply plenty of the alcohol to the adhesive tape from the reverse side of the main PCB. (Fig. 1) There is a hole on the PCB just under the LSI, and the adhesive tape can be seen through the hole. 3. Leave it more than one minute so that the alcohol weaken adhesive power fully. 4. Using a proper size of nozzle, apply heat to leads of the LSI with the desoldering machine. 5. Grasp the LSI with tweezers, and using gentle force vibrate the tweezers to feel melting solder. (Fig.2) 6. Remove the LSI after meltingsolder at every leads wholly.

H G

1 1 5 A

850 mV ± 20% 800 mV ± 20% 280 mV ± 20% 260 mV ± 20% 5200 mV ± 20% 5600 mV ± 20% 5.5 V

REPLACING THE DSP (HG51A115A01FD)

Spot Heater HS-600

Alcohl

1 5A

L S

Fig.1

Fig.2

�2�