20
AK19 CHASSIS MANUAL ADJUSTMENTS PROCEDURE
In order to enter the service mode, first enter the installation menu (or press blue button on the remote
control handset) and then press the digits 4, 7, 2 and 5 respectively.
For ADJUST settings:
Select
Adjust
using or button and press or button to enter it. To select different adjust parameters, use or button.
To change the selected parameter, use or button.
WHITE BALANCE ADJUSTMENT:
The following three parameters are used to make white balance adjustment. To do this, use a Colour Analyser. Using white point
RED, white point GREEN and white point BLUE parameters, insert the + sign in the square which is in the middle of the screen.
ADJUST 00
= White Point RED
ADJUST 01
= White Point GREEN
ADJUST 02
= White Point BLUE
AGC ADJUSTMENT:
In order to do AGC adjustment, enter a 60dBmV RF signal level from channel C-12.
Connect a digital voltmeter to pin 1 of the tuner. Change the AGC parameter until you see 3.70VDC on voltmeter display. Check
that picture is normal at 90dBmV signal level.
IF-PLL NEGATIVE ADJUSTMENT (Only with PLL tuner):
Connect 38.9 MHz test pattern for PAL B/G, PAL-SECAM B/G, 39.5 MHz test pattern for PAL I or 45.75 MHz test pattern for
PAL M/N, NTSC M model to Z401 SAW filter input terminals. Change the IF-PLL Negative parameter until you see IN, DOWN
below. If you cannot catch IN, DOWN position this way, using a screwdriver rotate the VIF-COIL LT401 left or right until you
see IN, DOWN.
IF-PLL POSITIVE ADJUSTMENT (Only with PLL tuner):
Connect 33.9 MHz test pattern for SECAM L model to Z401 SAW filter input terminals. Change the IF-PLL Positive parameter
until you see IN, DOWN below. If you cannot catch IN, DOWN position this way, using a screwdriver rotate the VIF-COIL LT401
left or right until you see IN, DOWN.
LUMINANCE DELAY ADJUSTMENT (with only TDA 8844 video processor):
Y-Delay PAL
Enter a PAL B/G colour and black-white bar test pattern via RF. Adjust Y-Delay PAL till the colour transients on the colour bar of
the pattern become as sharper and colours between transients do not mix with each other as possible.
Note:
If the SAW filter is one of the G1965M, J1951M, J3950M, K2958M, K2962M, G3957M, K6256K, K6259K or M1963M, there
is constant group delay distortion, so for an equal delay of the luminance and chrominance signal the delay must be set at a
value of 160nS. This means the adjustment must be set to the maximum value.
Y-Delay SECAM
Enter a SECAM B/G colour and black-white bar test pattern via RF. Adjust Y-Delay SECAM till the colour transients on the colour
bar of the pattern become as sharper and colours between transients do not mix with each other as possible.
Note:
If the SAW filter is one of the G1965M, K2958M, K2962M, G3957M, K6256K or K6259K, there is constant group delay
distortion, so for an equal delay of the luminance and chrominance signal the delay must be set at a value of 160nS.
This means the adjustment must be set to the maximum value.
Y-Delay NTSC
Enter an NTSC colour and black-white bar test pattern via RF. Adjust Y-Delay NTSC till the colour transients on the colour bar
of the pattern become as sharper and colours between transients do not mix with each other as possible.
Note:
If the SAW filter is M1963M, there is constant group delay distortion, so for an equal delay of the luminance and
chrominance signal the delay must be set at a value of 160nS. This means the adjustment must be set to the maximum value.
Y-Delay Other
In case of other colour systems, enter this system with colour and black-white bar test pattern via RF. Adjust Y-Delay Other till the
colour transients on the colour bar of the pattern become as sharper and colours between transients do not mix with each other
as possible. Normally for an equal delay of the luminance and chrominance signal the delay must be set at a value of 160nS.
This means the adjustment must be set to the maximum value.
VERTICAL ZOOM ADJUSTMENT (only for 110ø picture tubes):
Enter a PAL B/G circle test pattern via RF. Change vertical zoom till you see the upper and lower limit of the circle as close to the
upper and lower limit of the picture tube as possible.
VERTICAL SCROLL ADJUSTMENT (only for 110ø picture tubes):
Enter a PAL B/G circle test pattern via RF. Change vertical scroll till you see the circle exactly in the middle of the screen.
4:3 HORIZONTAL SHIFT ADJUSTMENT:
Enter a RED PURITY test pattern via RF.Change horizontal shift till the picture is horizontally centred. Check whether this adjust-
ment is correct after completing Service Mode Adjustment.
4:3 VERTICAL SLOPE ADJUSTMENT:
Enter a CROSS-HATCH B/G test pattern via RF. Change vertical slope till the size of squares on both the upper and lower part
of test pattern become equal to the squares laying on the vertical centre of the test pattern. Check and readjust VERTICAL
SLOPE item if the adjustment becomes improper after some other geometric adjustments are done.
