Tektronix PHASER 840 Quick Reference Manual page 86

4.
Turn on the printer and enable the PC diagnostics as explained in the
topic, "PC-based diagnostics" on the Phaser 840 Printer Service CD-
ROM.
5.
Run the
Purge Printhead Test
test suite. When the solenoid valve is energized, you should see the
vacuum gauge jump to about the value 51 cm Hg (20 in. Hg, 10 psi) and
within 4 to 6 seconds bleed off to 0.
If the vacuum does not reach the expected value:
There is a leak in the vacuum system from the pump
The accumulator and their plumbing or the vacuum pump is defective
If the vacuum drops to zero immediately, the cap/wipe/purge unit is
not sealed to the printhead.
This test allows you to check the action of the vacuum as it is applied to the
printhead; the cap/wipe/purge assembly should be sharply sucked against the
printhead faceplate. If it is not, there may be an ink clog in the vacuum tube
leading to the cap/wipe/purge assembly.
If the vacuum does not bleed off, then the air valve is not opening properly, the 7-
mil orifice (a part of the vacuum/pump assembly) is blocked or the vacuum
tubing may be clogged. If the printhead is hot, such a condition can allow ink to be
sucked into the vacuum system tubing. If the vacuum takes longer than 4 to
6 seconds to bleed off the cap/wipe/purge assembly is defective
If the vacuum bleeds off too quickly, then the cap/wipe/purge assembly is
defective; check to see if the cap/wipe/purge assembly is not sealing properly to
the faceplate. Check that the cap/wipe/purge assembly is properly positioned by
performing the "Cap/wipe/purge assembly belt adjustments" on page 68.
76 Phaser 840 Color Printer
from the
Head Maintenance