Poor Display Quality - DEC VR315 Service Manual

2–6 Troubleshooting
NOTE
Make sure the monitor has warmed up for at least 20 minutes
before you use Table 2–3.
Table 2–3 Poor Display Quality
Symptom Possible Cause
Poor geometry, Controls on top of the
centering, height, monitor are out of
width, and/or adjustment.
linearity.
Local magnetic fields.
Monitor is out of
adjustment.
Deflection module is
faulty.
CRT/chassis assembly
is faulty.
Poor light output The brightness or
(using the all-white contrast control is set
diagnostic pattern). incorrectly.
The Display is not
bright enough.
Host system is not
supplying correct
signal levels.
GAIN and Cutoff
adjustments may be
incorrect.
Video casting
assembly is faulty.
Deflection module is
faulty.
Suggested Solution
See section 4.1.
Remove any electro-
mechanical devices from
the vicinity of the monitor, or
move the monitor to another
location.
Perform the alignment
procedure. Refer to Chapter
4.
Replace the deflection module
(Section 3.2.4).
Replace the CRT/chassis
assembly (Section 3.2.6) only
after trying the previous
solutions.
Adjust the brightness and
contrast controls.
Repair the host system.
Perform the GAIN
adjustment (Section 4.6)
and the Cutoff adjustment
(Section 4.5).
Replace the video casting
assembly (Section 3.2.5).
Replace the deflection module
(Section 3.2.4).