Oki IP-6620 Maintenance Manual page 559

8.10.5 Power output voltage variability
The power supply unit output voltage can be adjusted with an output voltage variable button.
Use the 24VDC power supply with the default setting.
The 38VDC power supply is shipped with the voltage adjusted to 38.2 V ±0.3 V.
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OKI Data Infotech Corporation CONFIDENTIAL
Chapter 8 Operation Mechanism