Meaning: The above is a "left end alarm". The Left End Sensor (LES) failed to detect carriage arrival at the left end of its travel during the POST routine.
Possible cause: The cover interlock switch at the right front corner of the chassis isn't making. A brief explanation is in order.
The DL6400/6600 has two access cover interlocks:
a) On the upper edge of the control panel, there is a Hall-effect switch that's triggered by a permanent magnet embedded in the access cover. That device's output is a logic signal that merely informs the controller of the access cover's open/closed status.
b) At the upper right front corner of the chassis, there is a microswitch that's physically actuated by a plunger on the access cover. That switch is a safety feature. It disables the carriage drive circuitry when the cover is open. If the switch fails to make, the effect on the printer is loss of carriage motion. Hence the carriage can't get to its home position. Hence the machine reports a "left end alarm".
The microswitch is actuated indirectly via a spring-loaded pivoting paddle. In the case I came across, the actuator had gotten swung backwards and hung up on its bracket so it couldn't reach the switch. It just needed to be forced back into its correct at-rest position so it could operate as it should.
So, anytime you see a "left end alarm" on a DL6400/6600, examine the interlock switch first.
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