CTX 1995VL2X
Service Manual

1995VLX/VL2X/BLX

4.0 DESCRIPTION OF CIRCUIT The IC501(CPU) will detect polarity and frequency of input H.V. Sync.. The CPU will determine the mode of input timing (preset or users mode) and load mode data from IC502(EEPROM). The output of IC501 were connected to other function circuit (IE. H-size, H-phase, V-size, V-center�). Also, the user can adjust picture from keyboard and the data will be saved into IC502 automatically. For the O.S.D. mode, when O.S.D. manual is active CPU will inform the O.S.D IC (IC603) to send O.S.D BLK signal to blank the video signal from VGA card, and the O.S.D. IC will send O.S.D. R.G.B. Video signal to show the O.S.D. manual on screen. 6. H.V. regulation circuit The IC402 is a P.W.M IC, Pin7 is P.W.M output which connected to output transistor Q401 and Q402 via buffer driver Q407,Q409,Q410,Q408. The Q402 is H.V. output switching transistor, Q401 and D401 are damper device provide the path of damper current. IC401 is a feedback amplifier, the feedback voltage from FBT Pin11 connected to IC401 Pin5, and output is from pin1 which connected to IC402 for P.W.M the duty cycle control. 7. Video output circuit Video circuit consists of video preamplifier IC601 and output cascade amplifier IC604. IC601 is a video processing IC equipped with three DC amplifiers to pre-amplify R.G.B. signals from 0.7V to 4.2V. The R.G.B. GAIN & BIAS control signal are 2 from IC501 via I C-bus to DAC IC601. The IC601 control to video gain. The output of pin 24, 25, 26 are connected to BIAS circuit of each R.G.B. signal�s amplification and thus achieve a well balanceable white picture. The O.S.D. R.G.B. (Pin4, 9,13 of IC601) is the input of O.S.D. Video signal. The IC604 is R.G.B. drive to capable of driving CRT.

4.0 DESCRIPTION OF CIRCUIT
1. Power supply circuit The power supply is a serial & universal AC input switching power supply. The start up circuit (Q101) will provide a DC voltage for PWM (Pulse Width Modulation) IC(IC101) when power on. While IC101 works normal, Q101 will be cut off by the DC voltage. The IC101 will Auto-detect output voltage of power supply from Pin2 and correct the duty cycle of Pin6 output pulse to compensate the variation of output voltage. The output of IC101 Pin6 connected to power MOSEFET to drive the power transformer T101. When power MOSFET is on, the energy stored in the primary winding of T101. Once MOSEFET is off, the energy transfer to the secondary and charges the output capacitor to get the stable DC voltage. 2. Oscillation circuit The functions H-size, H-phase, V-size, Vcenter, Side-pin, Parallel�.are designed inside into IC301. The Pin2 is X-RAY protect input. When H.V output circuit is abnormal (H.V too high) the X-RAY protect circuit will shut off the horizontal output, H.V. also will be shut down. + The Pin6 is B control driver output. The Pin8 is horizontal square wave output drives horizontal output. The Pin11 is parabolic output. The Pin12,13 are vertical output. The Pin14 & pin15 are V-SYNC & H-SYNC input. The Pin17 is vertical blanking output. The Pin23,24 for vertical oscillator. The Pin28,29 for horizontal oscillator. The Pin30 is soft start. 3. Vertical output circuit The Pin12 & 13 of IC301 are vertical sync output connected to IC201 (Amplifier), Pin5 of IC201 is vertical amplifier output drives the vertical deflection directly. 4. Horizontal output circuit The DC-DC is to generate a DC voltage (B ) for horizontal output circuit. The CPU(IC501) controls the H. size adjustment function of 2 IC301 via the I C Bus. The output of IC301 (Pin6) connected to gate of Q311 to make the Q311 switching. When Q311 is ON, the energy stored in L305 and the energy released + via D313 when Q311 turned OFF. The B applied to Horizontal Yoke and supply the power for horizontal deflection. The more the + B ,will get the bigger the horizontal size. 5. CTX Micon circuit
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