CASIO ZX-556
Service Manual

PRECAUTIONS
To prevent damage of the thermal head caused by static electricity when assembling the chassis ass'y into the unit, the following steps must be followed; 1 : Turn the power switch off. 2 : Discharge the capacitor C5(2200µF) on the PCB Z556-1. 3 : Connect the FPC of chassis ass'y into a connector CN4 of PCB Z556-1. 4 : Assemble the chassis ass'y. 5 : Turn the power switch on.
LSI1 C5

CN4

FPC

PCB Z556-1 Chassis ass'y

ADJUSTMENT
Adjustment of low battery detection circuit

Figure-4

To adjust the threshold voltage of the low battery detection circuit, the following steps must be followed; 1 : Apply 9V to the battery terminals. Multi-meter-1 2 : Press ON while holding down 3 keys SET, RETURN and FUNCTION. (Start Diagnostic Program) 3 : Press 7.(Apply the voltage Vp for printer) 4 : Apply the voltage with a power supply so that the voltage at the collector of Q1 is 6.2V+0.1 / -0V. 5 : Adjust a pot VR1 so that the voltage between pin-8 of IC4 and pin-5 of IC3 is 0 +/-0.01V.
Multi-meter-2
0 +/-0.01V 6.2V+0.1/-0V

+
Power supply
VR1 IC4 5 8 IC3 Q1

+
9V ~ 6.5V

+

Figure-5

Setting the thermal head rank
Set the thermal head rank with pads RNK1 and RNK2 on the PCB L271-1 according to the following conditions when replacing the chassis ass'y or thermal head. The head rank is indicated on FPC as following figure-6. Head rank A : RNK1=SHORT, Head rank B : RNK1=OPEN, Head rank C : RNK1=OPEN, Head rank D : RNK1=SHORT, RNK2=OPEN RNK2=SHORT RNK2=OPEN RNK2=SHORT
XXXXXXB
Head rank = B
XXXXXXB

Figure-6

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