Tektronix Phaser 340 Service Manual page 123

5
Theory of Operation
Preparation. Following printer power-up from a cold start or in response to a
front panel menu selection, the print engine begins a printhead long cleaning
cycle. The first step is to stop any ink melting operation. Next, the main board
starts the heaters in the cap/wipe/purge assembly. The main board starts the
vacuum pump, which begins to create a vacuum in the vacuum accumulator.
The pressure in the accumulator is lowered to about 10.2 psi. It takes the
vacuum pump about 75 to 90 seconds to achieve this vacuum and then the
pump is shut off. Meanwhile, the printhead is tilted into the standby position, in
an action almost identical to the printhead tilt-to-print action described in the
earlier topic "Print process in operation" on page 5-18. In this case, the cam
follower follows the groove in the rotating cam gear, tilting the printhead
backward. Following the head tilt, the cap/wipe/motor rotates
counterclockwise to pull the cap/wipe/purge assembly into its cleaning
position. Next, the printhead is tilted forward slightly to seal against the
cap/wipe/purge assembly.
Purge.
Actual cleaning begins with the air valve solenoid energizing for
0.375 seconds; this momentarily routes the vacuum accumulator to the
cap/wipe/purge assembly and exposes the printhead faceplate to the vacuum.
The vacuum bleeds off after about 8 seconds through the 7 mil orifice. Then the
printhead is tilted backward to break the seal and the printer waits for 10
seconds for the waste ink to drain from the cap/wipe/purge assembly.
Long wipe. The cap/wipe/purge motor slowly rotates clockwise to pull the
cap/wipe/purge assembly's wiper blade down the face of the printhead, wiping
away ink and debris.
Long flush. The printhead is tilted back slightly and the cap/wipe/purge
assembly is raised to bring the wiper blade even with the jet nozzles. All jets are
fired for 10 seconds to flush air bubbles and foreign matter out of the jets. The
waste ink drips into the waste tray of the drum maintenance tray.
Dab.
The cap/wipe/purge assembly is lowered slightly and the printhead is
tilted forward to dab the wiper blade against the lower faceplate to clean ink off
the wiper. The cap/wipe/purge assembly is successively lowered slightly and
the printhead tilted back and forth four more times to dab the wiper blade.
Short wipe. Following the dab, the cap/wipe/purge assembly is raised and the
printhead is tilted forward against the wiper blade. The cap/wipe/purge
assembly is slowly lowered again to clean the faceplate but stops sooner, before
it can run into the debris from the first wipe.
Short flush.
The printhead is tilted back slightly and the cap/wipe/purge
assembly is raise to bring the wiper blade even with the jet nozzles. All jets are
fired again for 0.6 seconds.
Service Manual 5-31