Panasonic CT-25G6E Service Manual

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Panasonic CT-25G6E Service Manual Manual pdf 23 page image

- 23 -• C5: Drive_B . . . . . .803. Confirm using Black & White pattern and a whitescreen the color balance (gray scale and whitebalance). If white balance is required perform thefollowing:Procedure (Low Lights):1. Apply a Black & White pattern.2. Connect a jumper from the base of Q452 to coldground ( ) (or apply +2.5V DC to TP1 to defeatthe neck protector circuit).3. Set the Red and Blue Cut-Off registers (C0 andC2) to 00.4. On the Remote Control, press R-Tune to get agreen horizontal line.5. Connect the scope between GRN Cathode (GK, onthe CRT-Board) and cold ground ( ).6. View scope trace at Horizontal rate and adjust theService Mode DAC (C1) level until a scanningperiod of 195V above DC ground is measured, asindicated in Fig. 21.7. Adjust screen VR (on T551, Flyback) until thegreen line just becomes visible.8. Press R-Tune (on Remote Control) to display fullscreen.9. Select Red Cut-Off register (C0). Press R-Tune todisplay a green horizontal line. Increase C0 value(using Volume u) until the line turn yellow (mixinggreen & red).10. Press R-Tune to display full screen.11. Select Blue Cut-Off register (C2) and press R-Tuneto see the yellow line. Increase C2 value (usingVolume u) until the line becomes white (mixing redblue and green).12. Press R-Tune to display full screen.13. Confirm that a good gray scale is displayed whenviewing a Black & White pattern.14. EXIT the Service Mode.White Balance (High Lights)1. Using a Black and White pattern and white screenadjust Red Drive, C3, and Blue Drive, C5 to obtaingood white level on screen. If white looks reddish,decrease C3, if white looks bluish, decrease C5.2. Exit Service Mode.3. In Picture menu change Picture and Brightnessfrom low to high scales and observe black andwhite tracking.4. If corrections are required, repeat step 1 until thecorrect balance is achieved.5. Following satisfactory High Lights adjustmentperform the following White Balance Touch-Up.White Balance Touch-Up Procedure:Use this procedure to make minor adjustment to whitebalance.1. Enter Service Mode.2. Apply a black and white (B/W) signal (signal thatincludes gray tones).3. Observe low and high brightness areas of a B/Wpicture for proper tracking. Adjust the following asrequired for “good gray scale and warm highlights”:• HIGH LIGHT areas – Adjust Red Drive (C3) andBlue Drive (C5) registers until picture appear bestfor warm whites.• LOW LIGHT areas – adjust Red Cut-Off (C0) andBlue Cut-Off (C2) registers until best picture forblack-gray.Due to effect from low level adjustment on high leveladjustment, it is recommended that this procedure isdone at the end of the adjustments procedure.4. Exit Service Mode.5. Remove all external connections made to theReceiver.Sub-Brightness Final AdjustmentService DAC Adjustment (B2)This adjustment should be made last, followingother picture adjustments.Preparation:1. Turn the Receiver ON and allow 20 minute warmup at high brightness (white screen).2. Apply a black and white cross pattern.3. Set PICTURE to Max.4. Set BRIGHT to Center.Procedure:1. In Service Mode, select Sub Bright register (B2).2. Adjust B2 until the 7.5 IRE section looks same as3.0 IRE section as seen in Fig. 22.3. Exit Service Mode.Horizontal CenteringService DAC Adjustment (C9)Preparation:Connect a monoscope generator.Procedure:1. In the Service Mode, select the HorizontalCentering Adjustment DAC (C9). Adjust it untillocations “A” and “B” are even on both sides ofscreen, as indicated in Fig. 23.2. EXIT the Service Adjustment Mode.Figure 21. Cathode Waveform, AdjustmentWaveform Detail0V DC195VDCFigure 22. Sub-bright adjustment