HP 8753D Option 011 - Page 250

Test
Patterns
T
est patterns
are used
in the
factory for
displa
y
adjustmen
ts,
diagnostics,
and
troublesho
oting,
but
they
are
not
used
for
eld
service.
T
est patterns
are executed
by
entering
the
test
n
um
b
er
(66
through
80),
then
pressing
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EXECUTE
TEST
N
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CONTINUE
.
The
test
pattern
will b
e
displa
y
ed
and
the
softk
ey
lab
els
blank
ed. T
o exit
the test
pattern and
return the
softk
ey
lab
els,
press
softk
ey
8
(b ottom
softkey).
The follo
wing is
a
description
of
the
test
patterns.
66
T
est
pat
1.
Displa
ys
an
all
white
screen
for v
erifying the
light
output of
the
A18
displa
y and
chec
ks for
color purit
y
.
In
this,
and
other
solid
test
patterns,
an
extremely
thin
full-screen
horizon
tal
line
will
b
e
seen
ab
out
1/4
screen
heigh
t
from
the
b
ottom.
This
condition
is
c
haracteristic
of
the displa
y and
does
not indicate
an
y
problem.
67-69
T
est
P
at
2-4.
Displa
ys
a
red,
green,
and
blue
pattern
for
v
erifying
the
color purit
yof
the
displa
y
and
also
the
abilit
y
to
independen
tly con
trol eac
h
gun
color.
If
the
purit
y
of
the
display
ed test
pattern
is
a
problem,
it
usually
indicates
that
the
face
of
the
displa
y
needs
to
b
e
de-gaussed
(de-magnetized).
If
purit
y
is
bad,
cycling
the
p
o
w
er
a
few
times
ma
y
cure
the
problem. If
this do
es not
w
ork,
a
commercially
a
v
ailable
de-magnetizer
m
ust
b
e
used.
70 T
est
P
at
5.
Displa
ys
a
16-step
gra
y
scale
for
v
erifying
that
the
palette
c
hip
on
the
A19
GSP
b
oard
can
pro duce
16 dieren
t
amplitudes
of
color
(in
this
case,
white).
This
pattern
is
also
v
ery
useful
when
using
an
oscilloscop
e
for troublesho
oting. The
staircase
pattern
it
pro
duces
will
quic
kly
sho
w
missing
or
stuc
k
data
bits.
71
T
est
P
at 6.
Displa
ys
a
3-step
gra
y
scale
pattern
for
adjusting
the
bac
kground
lev
el
(or
0
step)
so that
the
rst
bar
is
not
visible,
and
the
second
bar
is
just
barely
visible.
This
pattern
consists
of
the
rst
three
gra
y
scale
bars
of the
16-step
gra
y
scale.
72
T
est
P
at
7.
Displa
ys
a
con
v
ergence
pattern
for
measuring
the
accuracy
of
the color
conv
ergence. It
is
mainly
for
use
b
y
the
factory
,
since
con
v
ergence
cannot
b
e
adjusted
in
the
eld.
73-74
T
est
P
at
8-9.
Displa
ys
crosshatc
h
and
in
v
erse
crosshatch
patterns for
testing color
conv
ergence,
linearit
y
,
alignmen
t,
and
high
v
oltage
regulation,
in
the
factory
only
.
No
eld
adjustmen
ts
are p
ossible.
75
T
est
P
at
10.
Displa
ys
an H
pattern for
chec
king the
fo cus
of the
displa
y
.
Under
normal
conditions,
this should
nev
er
need
to
b
e
adjusted.
Ho
w
ev
er, it
is
p
ossible
to
adjust it b
y accessing the fo cus con
trol adjustmen
t at the left rear of
the displa
y.See
the \Adjustmen
ts" c
hapter.
76 Test P
at 11.
Veries the functionalit
y of the pixel stretc
hing circuit of the A19
GSP b oard. Under normal conditions, this pattern should app ear all
white. If a
failure o
ccurs in the pixel stretc
hing circuit, the pattern will consist of 16 alternating
white and gra
yv
ertical strip es. Susp ect problems with the STRETCH line and
LFIRSTPIX.
77 Test Pat 12. Displays a rep eating gray scale for troublesho oting, using an
oscilloscop e. It is similar to the 16 step gray scale but is rep eated 32 times across
the screen. Each of the 3 outputs of the video palette will then show 32 ramps
(instead of one staircase) b etween each horizontal sync pulse. This pattern is used to
troublesho ot the pixel processing circuit of the A19 GSP board.
DRAFT
3/21/106 15:14
Service Key Menus and Error Messages 10-11
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