LG / GOLDSTAR FLATRON 795FT PLUS
Service Manual

DESCRIPTION OF BLOCK DIAGRAM
1. Line Filter & Associated Circuit. This is used for suppressing noise of power input line flowing into the monitor and/or some noise generated in this monitor flowing out through the power input line. That is to say, this circuit prevents interference between the monitor and other electric appliances. 2. Degauss Circuit & Coil. The degauss circuit consists of the degaussing coil, the PTC (Positive Temperature Coefficient) thermistor (TH901), and the relay (RL901). This circuit eliminates abnormal color of the screen automatically by degaussing the slot mask in the CDT when turn on the power switch. When you need to degauss while using the monitor, select DEGAUSS on the OSD menu. 3. SMPS (Switching Mode Power Supply). This circuit works with power of 110-240Vac (50/60Hz). The operation procedure is as follows: 1) AC input voltage is rectified and smoothed by the bridge diode (D901) and the capacitor (C907). 2) The rectified voltage (DC voltage) is applied to the primary coil of the transformer (T901). 3) The control IC (IC901) generates switching pulse to turn on and off the primary coil of the transformer (T901) repeatedly. 4) Depending on the turn ratio of the transformer, the secondary voltages appear at the secondary coil of the transformer (T901). The switch IC(IC903) contrals input-pulse-width and generates secondary voltage by sub-transformer (T903). 5) These secondary voltages are rectified by each diode (D906, D907, D908, D909, D910, D911, D912, D913) and operate the other circuits. (Deflection, Video Amplifier, etc.) 4. Display Power Management Circuit. This circuit control power consumption of the monitor by detecting H and V sync signal. There are stand-by and suspend mode. When no horizontal or vertical sync signal input, the circuit consists of Q930 and Q931 becomes stand-by and suspend mode. It�s power consumption is below 8W. When no horizontal and vertical sync signal input, it�s power consumption is below 3W. 10. Horizontal Deflection Output Circuit. This circuit makes the horizontal deflection by supplying the saw-tooth current to the horizontal deflection yoke. 5. X-ray Protection. This circuit detects the rectified DC voltage comes from the FBT pin 4. If the high voltage of the FBT reaches up to about 30kV (abnormal state), Micom(IC401) detects. It stops B+ voltage supplied to the FBT (T701), and high voltage is not be generated, (In the normal state, the high voltage is about 26kV.) 6. Micom(Microprocessor) Circuit. The operating procedure of Micom (Microprocessor) and its associated circuit is as follows: 1) H and V sync signal is supplied from Signal Cable to the Micom (IC401). 2) The Micom (IC401) distinguishes polarity and frequency of H and V sync. 3) The Micom controls each OSD function signals. (H-size, H-position, V-size, etc.) 4) The controlled data of each mode is stored in IC402. User can adjust screen condition by each OSD function. The data of the adjust screen condition is stored automatically. 7. Horizontal and Vertical Synchronous Processor. This circuit generates the horizontal drive pulse and the vertical drive pulse by taking sync-signal from Signal Cable. This circuit consists of the TDA4856(IC701) and the associated circuit. 8. D/D (DC to DC) Converter. This circuit supplies DC voltage to the horizontal deflection output circuit by decreasing DC 190V which is the secondary voltage of the SMPS in accordance with the input horizontal sync signal. 9. D/D Drive & Convert Circuit. This circuit is used for supplying B + voltage to horizontal deflection output transistor (Q709). This circuit makes to add side-pincushion correcting signal to B+ voltage.

- 15 -