Malata VT-600 portable VCD LCD screen troubleshooting - Power Circuits - Circuits

MOS power IC full range

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

One-piece inductor

(1) Inspection of backlight fluorescent lamps. As long as the circuit of this part is normal, the backlight fluorescent lamp can emit light after the power is turned on. It can be accurately judged by voltage measurement.

(2) Liquid crystal display and its driving circuit. First, measure the voltage of the four input terminals of the liquid crystal display: main power supply V∞+7.5V; 10-pin source power supply voltage VSH: +5.3V; 4-pin strobe power supply high voltage VGH: +16.5V ; (11) foot selects the pass power supply low voltage VGL; -9.5V. Secondly, it is determined whether the scanning timing circuit and the digital circuit in the inner periphery of the liquid crystal panel are normal. The method is: play a vcD disc, use an oscilloscope to detect whether the 2, 48, 47 feet of u3 and the 3rd input terminal of the display have a composite sync pulse (in the normal state, there should be a suitable composite sync at the above points). Pulse), and confirm whether the second and fifth terminals of the display have half-line pulse signals frpV, FRPT. If it does not exist, the internal timing circuit of the LCD screen is faulty. Finally, the oscilloscope is used to detect the three primary color signals. The observation points are: 6, 3, 9 of U3 (of course, it is necessary to confirm whether the 18 feet of U3 have a high level of +5.3v) and whether there are signals at the input terminals of 6, 6, and 8 of the display. At the same time, we must pay attention to 12 feet. In normal conditions, there should be a C0M signal.