Philips PTV800, Service Manual

Page: 82 / 567

GRAY SCALE AND BLACK AND WHITE TRACKING (G2 ADJ)
Note: Perform Electrical and Optical Focus before attempting this adjustment.
1. Remove the Light Barrier (if present) in order to view the Main Lens Output of each
picture tube.
Note: Any dust should be cleaned from the output lenses, mirror, and back of the screen with
a soft cloth.
2. Apply an NTSC Generator; display the Gray Scale Graduation Pattern. Or, if not
available, select a good channel containing high contrast program material.
3. Turn the set on and tune to the applied signal described in step 2.
4. Set the customer Picture control to ¾ range, set the Sharpness, Brightness and Tint mid-
range Place the customer Color setting at minimum.
5. Enter the Service Mode as explained earlier (0, 6, 2, 5, 9, 6, Menu). You will be at
register 00. At this point in the procedure, do not use the arrow key to scan the desired
register, instead use the random access key of the user remote and select 53.
Note: Scanning through or keying into register 04, Color Default, will turn the Color
back on to mid-range point. This Feature allows resetting customer color default
level before leaving the Service Mode.
6. Ensure the Cut-Off Registers (53, 54, and 55) contain the default value of 80. Correct if
necessary.
7. Ensure the Drive Registers (56, and 57) contain the default value of 40. Correct if
necessary.
8. Access Register 62 (G2 SETUP) and enter the value of "00" for the data held by that
register. The screen will go blank and all on-screen displays will disappear.
Note: This step places the cathodes of all three CRTs at 185Vdc. This is the optimum
condition to set CRT Cutoff.
9. Turn all G2 Controls (on the Screen/Focus control Block) to minimum (fully CCW).
10. Looking into the Output Lens, bring up each of the G2 (Screen) controls (bottom row the
Focus/HV Dist. Module) up to barely light each tube. Set as dim as possible, but make
the apparent brightness of each tube the same.
11. Press the Arrow Up Button once on the Remote Transmitter. The picture and on-screen
display will reappear.
REFINING GRAY SCALE AND BLACK AND WHITE TRACKING
1. Remove any color tint from the dark areas of the picture using the appropriate Cutoff
Control Registers (53, 54 and 55).
2. Remove tint from the Intermediate/Bright part of the picture using the Drive Control
Registers (56 and 57).
3. Confirm the color tracking by observing the Gray Scale while adjusting the Picture
Control from minimum to maximum range (high to minimum brightness). Adjust Cutoffs
and Drive control and defaults to obtain optimum performance.