Philips 20PT643F Service Manual page 57

5. Use the MENU LEFT/RIGHT keys to set the values of NORMAL RED, NORMAL
GREEN and NORMAL BLUE to '40'.
6. Press the MENU button twice to enter the normal user menu.
7. In the normal user menu, use the MENU UP/DOWN keys to highlight the
PICTURE sub menu (if necessary).
8. Press the MENU LEFT/RIGHT keys to enter the PICTURE sub menu.
9. Use the MENU UP/DOWN keys to select PICTURE. Be sure to record the
current value of PICTURE.
10. Use the MENU LEFT/RIGHT keys to set the value of PICTURE to '0'.
11. Use the MENU UP/DOWN keys to select BRIGHTNESS. Be sure to record the
current value of BRIGHTNESS.
12. Use the MENU LEFT/RIGHT keys to set the value of BRIGHTNESS to minimum
(OSD just visible in a dark room).
13. Press the MENU button twice to return to the top level SDAM menu.
14. Press the STATUS/EXIT button to hide the SDAM onscreen display.
15. Connect the RF output of a video pattern generator to the antenna input.
16. Input a 'black picture' test pattern to the television set.
17. Set the oscilloscope to 50 V/div and the time base to 0.2 milliseconds (external
triggering on the vertical pulse).
18. Ground the scope at the CRT panel and connect a 10:1 probe to one of the
cathodes of the picture tube socket (see schematic diagram B).
19. Measure the' cut off pulse' during the first full line after the frame blanking (see
Fig. 8-2). You will see two pulses, one being the 'cut off pulse' and the other
being the 'white drive pulse'. Choose the one with the lowest value; this is the 'cut
off pulse'.
20. Select the cathode with the highest VDC value for the alignment. Adjust the
Vcutoff of this gun with the SCREEN potentiometer (see Fig. 8-1) on the LOT to
the correct value (see table 8-1).
21. Press the STATUS/EXIT button to display the SDAM onscreen display.
22. Press the MENU button to enter the normal user menu.