Panasonic CT-25G6E Service Manual

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Panasonic CT-25G6E Service Manual Manual pdf 24 page image

- 24 -Vertical SizeService DAC Adjustment (C6)Preparation:Connect a monoscope pattern.Procedure:1. In the Service Mode, select the Vertical SizeAdjustment DAC (C6). Adjust until a perfect circleappears (Upper and lower sections of circle mayextend beyond the screen and therefore notvisible). See Fig. 24.2. EXIT the Service Adjustment Mode.MTS Circuit AdjustmentsThe MTS Circuit Adjustments require two steps:1. Input Level Adjustment.2. Stereo Separation Adjustment.Input Level Adjustment (M0)Preparation:1. Connect an RMS meter with filter jig as shown inFig. 25.2. Connect an RF signal generator to the RFantenna input.Procedure:1. Apply the following signal from the RF signalgenerator:Video: 100 IRE flat field, 30% modulation.Audio: 300Hz, 100% modulation, monaural(70 ±5dB, 75Ω OPEN, P/S 10dB).2. Adjust the MTS Input Level Adjustment (M0) untilthe voltage measured is 106 ± 6.0mV rms.Stereo Separation Adjustment (M1 & M2)Preparation:1. Connect an RF signal generator to the RF antennainput.2. Connect a scope to TPE10.Procedure:1. Select Stereo Mode in Audio menu2. Apply the following signal from the RF signalgenerator:Video: 100 IRE flat field, 30% modulation.Audio: 300Hz, 100% modulation, stereo (left only)(70 ±5dB, 75Ω OPEN, P/S 10dB).3. Adjust the MTS Low-Level Separation Adjustment(M2) until the amplitude displayed on the scopeis minimum.4. Apply the following signal from the RFsignal generator:Video: 100 IRE flat field, 30% modulation.Audio: 3KHz, 100% modulation, stereo (left only)(70 ±5dB, 75Ω OPEN, P/S 10dB).5. Adjust the MTS High-Level Separation Adjustment(M1) until the amplitude displayed on the scope isminimum. Repeat above steps 2 through 5 until theamplitude is at minimum for both signals.Clock Adjustment (X3)Preparation:Connect the frequency counter from TP5 (IC001Pin 11) to cold ground ( ).Note: Frequency Counter probe capacitance shouldbe 8pF or less.Procedure:1. Turn the Receiver “OFF” with the ACpower applied.2. Measure TP5 (IC001 pin 11) for the frequency ofthe waveform and record the reading.Note: Pin 11 measurement must have at least fourdigits of resolution following the decimal point.Example: 000.00003. Turn the Receiver back “ON”.4. Place the Receiver into Service Mode for makingelectronic adjustment, select the Clock AdjustmentDAC (X3).5. Calculate and set X3 based on the followingformula:Note: Pin 11 measurement will not changeregardless of the value stored in X3.Figure 23. Horizontal CenteringFigure 24. Vertical SizeTPE11Figure 25. Filter JigX3 128 0.9 6×10TP5 125–( ){ }125-----------------------------------+=