To measure, insert the positive (red) probe into the middle of the connector while at the same time touching the outside metal jacket.

The multimeter should read anywhere between 18.5-20 Volts DC. This is the normal operating range of the power supply, if it outputs less than 16 Volts or more than 20 Volts your power supply is defective.

If you read correct voltage but your printer is still malfunctioning, continue with the guide.