Ricoh DD 4450 - Thermal Head Voltage Adjustment

Master Feed
C279 4-48 SM
4.7.11 THERMAL HEAD VOLTAGE ADJUSTMENT
 This adjustment is always required when the thermal head or PSU has been replaced.
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")
 Read the voltage value on the decal on the thermal head.
1. Slide out the master making unit.
 Never turn VR1 clockwise rapidly while the master making unit is connected. The
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.
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.