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The lamp is not lit is a common fault . Projection lights must have three conditions : First, the good projection lamp ; Second, plus a ripple voltage across the lamp from the inverter circuit ( about 85V); Third bulbs should start early start plus a high-voltage pulse ( approximately 15kV, when you start the voltage modulation in terms of the breaking of the inverter circuit 85V supply voltage, the lamp is lit , the voltage disappears ) . Open the case , remove the ballast components, check the projection lamp is normal, the fault in the ballast inverter circuit or high voltage startup circuit . According to the three conditions of the lamp is lit , the first measurement of the inverter circuit 85V ripple voltage is normal , but when you start with a high-pressure test pencil near the site of the bulb without high pressure reaction , did not hear any " trace " sound produced when high pressure , indicating a fault in the high voltage startup circuit section. For this part of the local circuit shown in Figure 1 .yQMservice manual download site
As can be seen from the figure , 85V pulse voltage by the inverter circuit T1704 directly on the lamp while the high-voltage circuit through a start pulse is modulated on T1704 85V voltage within the specified time to start the lamp . Constitute a high-voltage pulse Q1710 and T1704 and other start-up circuit . At startup, the second integrated circuit IC1702 view broken timing control pulses applied to the gate of the switching field effect transistors Q1710 , Q1710 make work . T1704 primary signal current pulse after pulse voltage generated by the secondary diode to charge its internal capacitor. When the charging voltage is higher than 30kV, T1704 internal discharge device begins to discharge , so the output of the T1704 is able to generate a pulse voltage to 15kV . This voltage is superimposed on the 85V supply voltage of the lamp to start the lamp emits white light . According to the high-voltage generation circuit works, first of all voltage measurements Q1710 and found no voltage source . Check the source power supply circuit in turn , found R1726 (4.7Ω) open, with the same model troubleshooting resistance replacement.
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