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Troubleshooting 4-69
NovaJet 800 Series Service Manual
Initialization Failure
One symptom of a defective encoder sensor is when the carriage heads
fail to move during printer initialization - initialization does not complete
and a ‘Carriage Axis Error’ results. Replace paper sensor PWA on
carriage in this situation, unless the servo motor or trailing cable is proven
defective first. Another failure is characterized by erratic carriage
movement at power up, this is usually an unseated connection at the right
carriage PWA (offering the improper feedback to the servo system loop).
Carriage Tracking Failure
The infrared encoder sensor (on the right carriage) is responsible for
reading the encoder strip lines and providing feedback to the gate array
on the Main PWA and thus monitoring carriage position over 1000 times
per second and is responsible for exact ink drop placement onto the
media. The sensor uses binary counts to track carriage position along the
encoder strip, 4 basic counts are used = 00, 01, 10, 11. There are 150
lines per inch along the encoder strip, so (4 x 150 =) 600 dpi resolution is
achieved. However, home position is the left edge of media and should a
miscount occur then the image will ‘walk’ or skew from its intended print
position on each pass of the carriage head. Improper cleaning agents on
the encoder strip can cause encoder strip pitting to occur and thus lead to
miscounts. Encoder strips should be maintained in accordance with the
Routine Maintenance. If the encoder strip is not maintained then the ink
residue and air debris will transfer to the encoder strip causing it to fail.
Symptoms include failure of the carriage assembly to move at power up
(with ‘Carriage Axis Error’ displayed on the control panel display).
AutoLoad Paper Sensor Error
The Autoload-Paper sensor error only functions to pull media into the
printer. Triggered by the front edge of the media with a 6 second delay,
the sensor activates the stepper motor to drive the lower roller. Typically
the autoload paper sensor does not fail, it becomes nonoperational due to
ink covering Y-Arm surface or covering the LED (XMTR) or sensor
(RCVR). Initially clean the Y-Arm surface below the sensor with a
cotton swab or lint-free towel dampened with distilled water or isopropyl
alcohol, then remove the sensor and clean.