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COG LCD Display Of The DC Voltage

First of all, the LCD display switching power supply, COG LCD Display backlight circuit board + 14V and + 5.2 V two sets of output voltage detection, are normal. As the motherboard on the MCU can not start the normal work, resulting in the power board on the four-side regulator IC260 in the off state, this time no +12 V output, further check the motherboard +3.3 V voltage is only 1.2V, U1 (LD1117-3.3V) on the motherboard three-terminal DC voltage regulator detection, found its 3 feet of the input voltage of +4.5 V normal, measured its 2 feet output voltage of 1.2V, Significantly lower than the normal value of +3.3 V, which is judged to be + 3.3V DC voltage regulator damage. The internal + 3.3V is the standby voltage, converted from + 5.2V, mainly used for U3 (RTD2555LH) and U5 (RTD2120L) system reset, COG LCD Display standby, touch button power supply; this voltage is not normal will cause the machine Does not start, the machine used in the DC voltage regulator output current is too small, COG LCD Display after the damage can be used BM84-3.3 DC regulator direct replacement, the DC regulator maximum output current of 5A, its 1 foot For the ground terminal 2 feet for the output 3 feet for the input; with BM84-3.3 regulator directly after the replacement, but also must be removed D7,1N4007 diode, put a current 3A 3A 1N5408 diode. After switching off the power to see the display panel on the LED light on the first light, COG LCD Display immediately turn green, then in the middle of the LCD screen appears "no signal input, please check the signal line" green dialog box, 5 Seconds after the disappearance of the host computer to connect the signal line after the liquid crystal display to resume normal work.

LCD monitors are equipped with two-channel audio amplifier, built-in two 0.5W8Ω speaker, the monitor has a volume size and mute the function of the program keys, first on the LCD monitor motherboard stereo audio amplifier U9 (SA7496L) Detection and found its 15 feet, COG LCD Display 16 feet of the supply voltage is only 0.6V, COG LCD Display the monolithic two-channel power amplifier maximum output power of 2W +2 W, the normal operating voltage of +12 V, after the power, backlight circuit board Output +12 V detection and found that the output voltage is 0.6V, first check the audio amplifier SA7496L peripheral components without exception, suspected failure may be out on the +12 V regulator (see Figure 2); COG LCD Display after IC260 (PQ12RD21 ) PQ12RD is a 12V four-terminal regulator, when the 4 feet On the high level when the output turn on, from the 2 feet output +12 V voltage supply audio amplifier;

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