Davin J012, Service Manual

Page: 326 / 365

The vertical motor [1] drives the timing belt [2] that rotates the transport roller [3].
The rotation of the transport roller also drives the paper feed roller when the paper feed clutch engages
the feed roller (not shown above).
The edge of the vertical encoder [4], attached to the shaft of the transport roller, passes through the gap
of the vertical encoder sensor [5] as the encoder wheel rotates. The vertical encoder sensor reads the
coded markings on the rim of the vertical encoder and sends this information to the CPU. The CPU uses
these readings to control the on/off timing of the transport belt and the paper feed roller:
• When servicing the machine, work carefully to prevent scratching, breaking, or bending the vertical
encoder wheel.
Paper Path
Here is a summary of the operation that sends paper through the printer:
1. The feed clutch energizes and engages the feed roller, then the rotation of the vertical motor drives
the feed roller.
2. Paper feed roller feeds 1 sheet from the top of the stack in the paper cassette. A friction pad at the lip
of the paper cassette prevents double-feeding.
3. The charge roller charges the transport belt. The electrostatic charge on the transport belt keeps the
paper on the transport belt.
4. The sheet feeds onto the transport belt.
5. The feeler of the trailing edge sensor depresses and switches the trailing edge sensor on.
6. When the trailing edge sensor goes on, the carriage moves to the right of center. This lets the 1st
registration sensor detect the leading edge of the paper.
7. The 1st registration sensor also detects the right edge of the sheet when the carriage and sensor move
toward the carriage HP sensor on the right.
8. The detection of the right edge by the 1st registration sensor is used to determine the width of the
paper in the paper path.
• The 1st registration sensor reads the right edge of only the 1st sheet of the print job. Thereafter,
the 1st registration sensor does not right edge for any until the beginning of the next print job.
9. An area equal to the length of each print head gets printed when the carriage goes across the sheet
from right to left.
10. When the last line prints, the transport roller rotates only long enough to feed the length of the last
sheet.
11. The print job count increases by 1 after the paper exits.
Paper Feed, Transport, Paper Exit
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