SAMSUNG ML2571
Service Manual

I THEORY OF OPERATION
GENERAL This is a h�lg h- resolution monochrome display monitor � using a paper-white phosphored CRT with etched. faceplate. uses one video signal input and seoarare sync signals. 0 can operate in all of the VGA modes. It Because of the losses in the deflection yoke. a linearity correction is required. This is achieved by L302. The horizontal screen size can be varied by adjusring ~303. The high voltage of 12.5KV for CRT anode is also generated in flyback transformer by use of flyback pulse. l-4. Vertical Processor IC 201 DESCRIPTION ICI201 performs following functions. 1. Main Board l-1. Power Supply This is a constant-frequency switch-mode power supply using l-4960 monolithic integrated circuit. The output voltage regulation is achieved by means of variable duty cycle. The output voltage of this power supply is fed back into the pin 2 of l-4960. This voltage is compared to reference voltage internally. The difference of these voltages control the duty cycle of output current. 0401 to D404, and C404 to C405 form input dc supplier. C408, C409, R404 are the components for frequency compensation, R403, C406 are for oscil!stion of sawtooth wave. C407 is for soft star: of this circuit. 0405 is a flywheel diode for ccntinuous current flowing. Output voltage is varied by adjusting VR401 potentiometer. 2 . CRT Boar;&e&al, oscillator - Ramp generator - Linearity control - Output amplifier There are three vertical size dontrol : VR202. VR203, and VR204. VR202 is for mode 3, VR2113 for mode 2. and VR2O4 for mode 1. Each mode is automatically seiected by IC301.

l-5. Dynamic Focus Cl501 is used to provide dynamic focus voltage which is added to G4 voltage of the CRT. This voltage is needec to change�G4 voltage according to tlie angle of the beam

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Horizontal Processor tC302

IC302 performs following functions. - Horizontal oscillator - Phase-locked loop for frequency acd phase comparison. - Phase-locked loop to compensate various delay times of the horizontal output transistor.

IClb1(M51392P) contains wide bandwidth video amp! fier, gain control, pedestal clamp and brightness conrrcircuits. Cl103 and Q104 form a cascade video ampiifie. circuit which output is applied to cathode pin of tin CRT.

3. Line Filter Board This board contains fuse and EMI filter componefl=

The sync signal from Q303 is fed info pin 3 of IC302, and flyback pulse into pin 4. This two signals are compared and the circuit is locked to a correct frequency and phase.

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IMPORTANT : When replacing the power supply, mat:: sure that the green/yellow ground w:is properly attached to the main chas:: frame. When replacing -he fuse, mari sure that the fuse is of the same ty=* and rating as the originai.

l-3. Horizontal Output Stage Cl305 6305 is a horizontal output switch which is closed during the scan period and opened during the flyback. It sinks a drive signal from IC302 through 04. The flyback period is determined by the resonance of C316 and deflection yoke. C316 makes the necessary S-correction.

*NOTE : The adjustment requires the connection of a pe_;rr~ computer to the monitor. Although the man:: : adjusted before it is delivered, readjustment ma* :Z 4 required when the setting position is changed Ot.K+ a component is replaced.

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