Alignments - Philips A02U AA Service Manual

8. Alignments

Index of this chapter:
1. General alignment conditions
2. Hardware alignments
3. Software alignments
4. Option settings
8.1
General Alignment Conditions
8.1.1
Default Alignment Settings
Perform all electrical adjustments under the following
conditions:
•
Power supply voltage: 120 V_ac / 60 Hz (± 10 %).
•
Connect the set to the mains via an isolation transformer
with low internal resistance.
•
Allow the set to warm up for approximately 20 to 30
minutes.
•
Measure voltages and waveforms in relation to chassis
ground (with the exception of the voltages on the primary
side of the power supply). Caution: never use heatsinks as
ground.
•
Test probe: Ri > 10 Mohm, Ci < 20 pF.
•
Use an isolated trimmer/screwdriver to perform
alignments.
Perform all electrical adjustments with the following default
settings (for all CRTs):
•
Choose "Weak" picture mode with the (Smart) "Picture"
button on the remote control.
•
Set "Dynamic Contrast" (accessible via MENU ->
PICTURE) and "Active Control" (on remote control) to "off"
(if either one of them is present).
•
Set "Brightness" (accessible via MENU -> PICTURE) to
aligned value unless otherwise specified.
8.1.2
Adjustment Sequence
Use the following adjustment sequence:
1. Set the correct TV-set OPTIONS as described in
paragraph "Options". After storing, re-start the set.
2. Rough adjustment of VG2 and FOCUS.
3. RF-AGC alignment.
4. IF-PLL OFFSET adjustment.
5. Rough adjustment of GEOMETRY.
6. Allow the set to warm up.
7. Precise adjustment of VG2 and FOCUS.
8. Precise adjustment of GEOMETRY.
9. PIP alignments (if present).
10. COLOR alignments.
11. Other software alignments.
8.2
Hardware Alignments
Notes:
•
The Service Alignment Mode (SAM) is described in chapter
5 "Service Modes, Error Codes, and Fault Finding".
•
Use the cursor-, menu-, and OK-buttons of the remote
control (RC) transmitter for navigation.
Alignments A02U AA
TUNER
CINCH I/O
Figure 8-1 Top view LSP
8.2.1
Vg2 Adjustment
Notes:
•
For adjusting the Vg2 in A10 sets, the vertical scan had to
be disabled by the VSD bit (Vertical Scan Disable).
However, do not use this option in this chassis (when
present, because not used in all software), as it will lead to
a "beam current" protection!
•
Also, the option "VG2" in the SAM does not function yet.
Please, do not use!
In the frame-blanking period of the R, G, and B signals applied
to the CRT, the video processor inserts a measuring pulse with
different DC levels. Measure the black level pulse during the
vertical flyback at the RGB cathodes of the CRT.
1. Connect the RF output of a pattern generator to the
antenna input. Input a "black" picture (blank screen on CRT
without any OSD info) test pattern.
2. Use the MENU key to enter the "user" menu, select
"Picture", and set "Brightness" and "Contrast" to minimum
(write down the original settings).
3. Set the oscilloscope to 20 V/div and the time base to 20 us/
div. Use external triggering on the vertical pulse (caution:
use a trigger point on the "cold" side!)
4. Ground the scope on the CRT panel ("cold" side) and
connect a 10:1 probe to one of the cathodes of the picture
tube socket (see circuit diagram F).
5. Measure at test points F017, F018 and F019 on the picture
tube socket (or pins 6, 8, and 11) the DC-level of the
measuring pulse (1st full line after the frame blanking) with
respect to earth.
6. Select the pin with the highest level found and adjust
V_cutoff by means of the Vg2-potmeter (lowest-one) on the
Line Output Transformer (LOT) to 165 +/- 5 V_dc (for all
screen sizes).
7. Reset "Contrast" and "Brightness" to their original values
(as written down).
max.
0V Ref.
Figure 8-2 Waveform Vg2 alignment
8. EN 89
1502
B
Warning
All alignments
are on hot-part !
5430
C
LOT
Focus 1
Focus 2
Screen
VG2
3642
A
V.SHIFT
E_13950_061.eps
120304
V [V ]
CUTOFF DC
E_06532_011.eps
110204