25
107P2 CM25 GSIII
Electrical Adjustments (Continued)
8. Focus adjustment
9. Loading DDC code
10. To access service mode
Apply a signal of " @ " character. at 68.7 kHz/85 Hz mode set the
brightness to mid-position , contrast to max - position and adjust
the focus for optimal sharpness in the area within 2/3 from the
screen center.
The DDC HEX data(refer sheet 190) should be written into the
EEPROM (7804) ,0~127 bytes by EEPROM writer or equivalent
method.
The service mode is for service purpose which convenient to
perform repair service and pre-warm up monitor before test or
re-adjustment colour temperature without any video signal
generator requirement.
10.1 Remove video signals
10.2 Press "
" and "
" simultaneously on the front control
panel ,then press "
",release all bottons till the full white
pattern come on the screen of monitor.
10.3 In the beginning of service mode (full white pattern), the monitor
will working at 48kHz of horizontal frequency, after 55 seconds,
it will switch to 81kHz automatically, then change mode between
two modes constantly every 55 seconds.
10.4 You may quit service mode by either turn off and on or feed
video signals to the monitor.
11. Purity adjustment
12. Static convergence
- Make sure the monitor is not exposed to any
external magnetic field.
- Produce a full red pattern on the screen, adjust the
purity magnet rings on the PCM assy (on CRT) to
obtain a complete field of the color red. This is done
by moving the two tabs (2-pole) in such a manner
that they advance in an opposite direction but at
the same time to obtain the same angle between
the two tabs, which should be approximately 180
degree.
- Check by full green pattern and full blue pattern
again to observe their respective color purity.
Introduction
Slight deviation in the static convergence can be
corrected by using two permanent pairs of magnets
which are fitted around the neck of the CRT. These
are the 4-pole magnet and the 6-pole magnet.
The 4-pole magnet move the outermost electron
beams (R and B) parallel in the opposite direction
from the other. The 6-pole magnet moves the
outermost electron beam (R, B and G) parallel in the
opposite direction from the other.
The magnetic field of the above magnets do not affect
the center of the CRT neck.
2-pole purity magnet
6-pole convergence magnet
4-pole convergence magnet
Deflection Yoke
4-pole
Beam motion producced by the
4-pole convergence magnet
S
S
N
N
B
G
R
S
S
N
N
B
G
R
Beam displacement
direction
Magnetic flux
lines
6-pole
Beam motion producced by the
6- pole convergence magnet
S
S
S
N
N
N
R
B
G
S
S
S
N
N
N
R
B
G
Setting
- Before the static convergence setting can be made,
the monitor must be switched on for 30 minutes.
- The focus setting must be made correctly.
- Signal: 640 * 480, 31.5 kHz/60 Hz mode.
- Set the tabs of the 4-pole magnet in the neutral
position. This is when the tabs are opposite one
another. In this position the magnets do not affect the
deflection of the R and B electron beams.
- Set the tabs of the 6-pole magnet in the neutral
position. This is when the tabs are opposite one
another. In this position the magnets do not affect the
deflection of the R, B, and G electron beams.
- First set the 4-pole magnet optimally.
- Then set the 6-pole magnet optimally.
- If the convergence is not now optimal, then adjust to
the optimal setting with the 4-pole magnet and then with
the 6- Pole magnet again.
- Set the tabs of the 6-pole magnet in the neutral
position. This is when the tabs are opposite one
another. In this position the magnets do not affect the
deflection of the R, B, and G electron beams.
- First set the 4-pole magnet optimally.
- Then set the 6-pole magnet optimally.
- If the convergence is not now optimal, then adjust to
the optimal setting with the 4-pole magnet and then
with the 6- pole magnet again.
