Panasonic CT-25G6E Service Manual

Also see for CT27G6DE - 27" COLOR TV: Operating instructions Service manual

Panasonic CT-25G6E Service Manual Manual pdf 22 page image

- 22 -Service Adjustments (Electronic Controls)Note: It is recommended to allow for a 30 minutewarm up period, at high brightness level (usewhite screen), prior to any picture adjustment.Sub-ContrastService DAC Adjustment (B3)This adjustment is factory set. Do not adjust unlessrepairs are made to associated circuit, the CRT Boardor when the CRT is replaced.Preparation:1. Apply a color bar signal pattern with 87.5%modulation, 70% saturated color bar with a 100IRE white and 7.5 black.Note: The pattern used in this procedure is an EIA colorbar pattern with 87.5% modulation with 100 IREwhite and 7.5 black. Correlate the information in thisprocedure to the pattern used if another signalis used.2. Preset the following controls:• Brightness . . . . . . . Center.• Picture . . . . . . . . . . Max.• Sharpness . . . . . . . Center.• γ Gamma (S5) . . . . 15• ACL OFF (CA) . . . . 00• Cut Off G (C1) . . . . 003. Connect the oscilloscope to the CRT-Boardconnector C1-2 (TP35). Set the scope time base to20μs (horizontal).Procedure:1. In the Service Mode, select DAC Sub-ContrastAdjustment (B3) and adjust for 2.5 ±0.1Vp-pbetween white and black level. (See videowaveforms detail, Fig. 18).2. Following adjustments set S5, CA & C1 to theiroriginal settings.3. Turn Receiver OFF and disconnect test equipment.Sub-BrightnessService DAC Adjustment (B2)Due to the characteristics of this chassis, Sub-brightness adjustments are not necessary. For goodbrightness level set the register to “127”, the defaultlevel.Perform “Sub-Brightness Final Adjustment” on page 23only if a different brightness level is required for thepicture.Tint/Color AdjustmentService DAC Adjustment (B1) (B0)Preparation:1. Apply a rainbow color bar signal.2. Preset the following controls:• Brightness . . . . . . . Min.• Color . . . . . . . . . . . Center.• Tint. . . . . . . . . . . . . Center.• Picture . . . . . . . . . . Max.• Sharpness . . . . . . . Min.• γ, Gamma (S5). . . . 15• ACL OFF (CA) . . . . 003. Connect the oscilloscope to TP37 (or C1-3).Procedure:1. In the Service Mode for making electronicadjustments, select DAC Sub-Tint Adjustment(B1). Adjust until the waveform measured is as theone shown in Fig. 19.2. Connect the oscilloscope to TP35 (C-Board) andGND.3. Select DAC Sub-Color Adjustment (B0) and adjustfor peak to peak amplitude to be 0.8Vp-p ±0.05Vas shown in Fig. 20.4. Following adjustments, reset controls modifiedduring preparation to their original levels5. Turn Receiver OFF and disconnect test equipment.White BalanceService DACs. (C0) (C1) (C2) (C3) (C4) (C5)Preparation:1. Turn the Receiver “ON” and allow 30 minuteswarm up at high brightness (white screen).2. Preset the following DACs:• C0: Cut Off_R . . . . 0 255• C1: Cut Off_G . . . . 0 255• C2: Cut Off_B . . . . 0 255• C3: Drive_R . . . . . . 80• C4: Drive_G . . . . . . 80Figure 18. TP35 waveform2.5V p-p ±0.1VFigure 19. TP37 waveformTP47B (A-Board)Figure 20. TP35 waveformTP35 (C-Board)0.8Vp-p±0.05V