Thermal Head Voltage Adjustment - Ricoh DD 4450 Service Manual

Master Feed

4.7.11 THERMAL HEAD VOLTAGE ADJUSTMENT

This adjustment is always required when the thermal head or PSU has been replaced.
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Purpose: To maintain master making quality and extend the lifetime of the thermal head.
Standard: Refer to the voltage value (X) printed on the thermal head. The value varies from one
thermal head to another.
The adjustment voltage should be between X and X - 0.1 V.
Tools: Circuit tester
Left cover ( p.4-9 "Left Cover")
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Read the voltage value on the decal on the thermal head.
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1. Slide out the master making unit.
Never turn VR1 clockwise rapidly while the master making unit is connected. The
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T/H will be damaged if too much voltage is supplied suddenly.
2. Connect the positive terminal of a circuit tester to TP701 and the negative terminal to TP702.
If the output and ground terminals touch each other, the board will be damaged.
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3. Connect the power plug, and turn on the main switch to access SP mode.
4. Select SP5-12 (VHD signal).
5. Press the Start key. Power is continuously supplied to the thermal head, so press the Stop
key if you cannot finish the adjustment quickly.
6. A beeper sounds while the power is being supplied.
7. Measure the voltage, and turn RV1 so that the value becomes between "+0" and "-0.1" volts
from the value on the thermal head decal.
C279 4-48 SM