Grundig ST 55 - 750 Text Servicehandbuch Seite 29

CUC 7350
GB
Alignment
All adjustment controls not mentioned in this description are adjusted during production and must not be readjusted in the case of repairs.
Measuring Instruments: Dual-channel oscilloscope with 10:1 test probe, colour signal generator, high resistance voltmeter
Cecks and adjustments after replacement or repair of:
Power Supply: 1.
Horizontal Deflection: 3., 8.
CRT-Panel: 3., 6.
IF Amplifier, Tuner: 4., 5.
Vertical Deflection: 8.
Feed in the test patterns via HF and store them at programme position 1.
For adjustments 4. thru 8. the Service Menu must be called up.
Calling up the Service Menu: Switch the TV on while holding down button " " for ≥ 3 seconds.
Alignment
1. +A Voltage Brightness: mimimum.
Voltmeter: cathode D61001.
2. Line sharpness Feed in the convergence test pattern.
Contrast to maximum.
Set the brightness so that the black background of the test
pattern is just brightening.
3. Screen grid Feed in the grey scale pattern.
voltage U Contrast ( ) minimum.
SG
Colour contrast ( ) minimum.
Adjust the screen brightness ( ) so that the gradation from
the darkest grey to the black bar is just still visible.
Measure the R,G,B test points to determine the point at
which the black level is highest and connect the
oscilloscope.
4. Tuner-AGC Feed in a standard test pattern on a channel in the upper
range of the UHF band and store it at programme position
1. HF ≥1.5mV (64dBµV, noise-free picture).
Switch the TV off with the mains button.
Voltmeter: tuner contact 2
Call up the Service Menu with button " " (see above).
With
5. AFC-Reference Tune in a local station with standard channel spacing
without fine tuning at the desired programme position on
a channel as low as possible.
Call up the Service Menu with button " " (see above).
With
6. White balance Feed in the FuBK test pattern –> Colour contrast ( )mini-
mum –> Contrast ( ) maximum.
Adjust the screen brightness ( ) so that the gradation from
the darkest grey to the black bar is just still visible.
Call up the Service Menu with button " " (see above).
With
Select alignment function 5 or 6 with
GRUNDIG Service
Preparations
select the line "AGC ALIGN" in the menu.
select the line "AFC ALIGN" in the menu.
select line "TV PROCESSOR".
With control R60037 set the voltage to 115V (14" Orion ),
105V (14" Philips), 124V (15...21").
With the focus control at the line transformer adjust the
horizontal lines for maximum sharpness.
With the control SCREEN at the line transformer (below
the focus control) set the black level at the test point with
the highest black level to 100...105V for 14" and to
155...160V for 15...21" picture tubes.
With the buttons
or:
With the buttons
just starts to appear in the picture. Then tune in the reverse
direction until the picture just becomes noise-free.
On activation of AFC Reference, IC80000 adjusts the AFC
mid-value (the characters AFC ALIGN become white) and
stores this value in the memory IC87060.
If the characters are yellow (value is not correctly aligned)
correct the AFC using filter F33025. Repeat several times
if necessary. The arrows
AFC value in the menu indicate the sense of rotation for
this filter alignment.
Note:
The AFC voltage is used on station search as a comparative
value for VCR-HF playback (station identification "AV") to
readjust the modulator drift.
With the buttons
Green (5) and White Point Blue (6) so that no colour is
visible in the test pattern. The values are stored
automatically.
.
Abgleich / Alignment
Alignment Process
Schwarzwert
Black level
105-110V
100...105V 14"
155...160V 15...21"
±
and set the voltage to 3.3V
and tune the TV station so that noise
on the left and right of the
set the values for White Point
0.4V.
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