BenQ PB8250 Service Manual page 73

If we line the x and y, then the Pb offset is the shift action and the Pr offset is the rotational action.
(3) Connect power, YPbPr Video into projector.
(4) Change Timing and pattern of pattern generator :
Timing : 480P(H:31.54 KHz,V:60.08 Hz)
pattern : black
(5) Light on projector
(6) Set user OSD values to default.
(7) Enter factory mode.
(8) Set Factory values to default.
(9) Follow the PbPr offset adjustment flow chart:
Case
x1>x0 & y1>y0
Decrease Pb offset
until x<=x0 or
y<=y0
A
Case x<=x0:
The value note (x2,y2). The value note (x2,y2).
Dy = y2 - y0.
Decrease Pb offset until the y Decrease Pb offset until the x
value <= y2 - 1/2Dy . Now, the value <= x2 - 1/2Dx . Now, the
reading of the Lux meter = reading of the Lux meter =
(x3,y3) and x3 will < x0, y3 will (x3,y3) and x3 will > x0, y3 will
> y0.
Decrease Pr offset the x value Increase Pr offset the x value will
will increase and y value will decrease and y value will increase
decrease to meet the spec.
B C
Case y<=y0: Case x>=x0:
The value note (x2,y2).
Dx = x2 - x0. Dy = y0 - y2.
Increase Pb offset until the y
value >= y2 + 1/2Dy . Now, the
reading of the Lux meter =
(x3,y3) and x3 will > x0, y3 will
< y0. < y0.
Increase Pr offset the x value will
decrease and y value will increase
to meet the spec. to meet the spec.
Use Lux meter to
read the coordinate of
black and the value
note (x1,y1).
Case
x1<x0 & y1<y0
Increase Pb offset
until x>=x0 or
y>=y0
D
Case y>=y0:
The value note (x2,y2).
Dx = x0 - x2.
Increase Pb offset until the x
value >= x2 + 1/2Dx . Now, the
reading of the Lux meter =
(x3,y3) and x3 will < x0, y3 will
> y0.
Decrease Pr offset the x value
will increase and y value will
decrease to meet the spec.
72
Case
x1>x0 & y1<y0
Increase Pr offset until
x<=x0 or y>=y0
Case x<=x0: Case y>=y0: Case x>=x0:
C B
Case
x1<x0 & y1>y0
Decrease Pr offset
until x>=x0 or y<=y0
Case y>=y0:
A D