Zenith A50M84D Series Service Manual Download

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CM150/PV150

3-6

GM CHASSIS

SERVICING

To set G-2 place the G-2 set up jumper (SW1), the jumper
is on the rear left corner of the main module, place
jumper into setup position. The G-2 adjustment controls
are found in the back of the projo cabinet above the
large signal module, in a black plastic block.
Adjust the green G-2 control clockwise until you just
begin to see the vertical retrace lines (lines going from
the lower left up toward the upper right side). Now
repeat the same procedure for the red and blue G-2
settings. Return the G-2 setup jumper (SW1) to the
normal position.

Focus Setup

There are two focus controls, mechanical (on the lens
assembly) and electrical (focus pots next to the G-2
pots). This procedure should be done using generator
and a cross hatch or other pattern that fills the display
with a horizontal and vertical pattern. Focus one color
at a time. Use the video cutoff jumpers to disable the
video display of the other two CRTs.
Setup the mechanical focus giving your attention to the
center area of the display. Setup the electrical focus
giving your attention to the area between the center
and the outer edge of the display. You may have to
repeat the steps several times to achieve correct focus.
Take time to do it correctly as focus will affect
convergence setup.

Yoke Ring Magnets (Read Convergence Procedure
first)

Use a cross hair signal for this adjustment. Before

adjusting the yoke ring magnets make sure that the yoke
is pushed tight up to the bell of the CRT. In projection
systems the yoke is only adjusted for tilt and
uncorrected center beam landing. The proper alignment
of the tilt and beam landing is necessary for proper
convergence. If yoke alignment is incorrect conver-
gence alignment will become more difficult. You may
cause some of the convergence controls to run out of
adjustment range. A cross hair test pattern is the best to
use for yoke alignment.

The GM chassis convergence is controlled by the remote
control. To put the projection system into the conver-
gence mode press and hold the

MENU

key, until the

customer menu display disappears, then press

999

ENTER

. Now disable convergence by pressing

PIP

for

TRK4000

FREEZE

for

MBR

remote. Disabling conver-

gence will allow you to see where the uncorrected CRT
beam landing is.
Check the three yokes for tilt. Loosen the yoke clamp if it
is necessary to adjust the tilt. The red, green, and blue
vertical lines should be parallel to each other and
vertical to the screen frame. Do this adjustment
carefully as it will affect the convergence controls. It is
best to measure the distance between edge of the
screen frame and the top of the center line. Now
compare it to the same measurement at the bottom of
the center line to the screen frame. When the two
measurements are equal the yoke tilt adjustment is
correct.
Be careful not to over tighten the yoke clamp. It should

Red

Green

Blue

Center Reference

be just snug enough so the yoke will not move. If it is
over tightened it may break the CRT neck.
Adjust the green ring magnets so cross hair pattern is at
the display center (measure the screen frame opening to
find the center point). Adjust the red yoke ring magnets
so the red horizontal center line is converged to the
green horizontal center line and the red vertical center
line is to 3/4" the right of green vertical center line.
Adjust the blue yoke ring magnets so the blue horizontal
center line is converged to the green horizontal center
line and the blue vertical center line is to 3/4" the left of
green vertical center line. Once all three CRT ring
magnets have been adjusted press

PIP

for

TRK4000

FREEZE

for

MBR

remote, to enable the convergence

correction to the display. For futher convergence
information prefer to touchup convergence page 2-4.

G-2
Setup

BLUE

GRN

RED