Question about Sony Televison & Video
Have you a digital multimter that can count frequency. if so the testing will be easier to you. Just count the requency at the collector point of horizontal driver transistor, or at the base of horizontal output transistor. it should come around 15.625KHz [15625Hz]. When the tv wors with no signal this frequency may differ, but come very near to it. When it synchronises with a picture, it won't vary and will remain constant.
If you have no frequency counter, just measure the voltage at the collector of horizontal driver transistor. It will be normally connected to the primary winding of the line drive transformer, which is very small transformer on the PCB. Then check the voltage at the other end of that trnsformer, where supply to the collector of the above said trasistor is given. The voltage at the collector side of the winding and at the other side of the winding must have some difference, if the frequency said above is present, and drive transistor is working.
If there is no voltage, check the resistor connected to that winding to main power supply for open, or the capacitor fitted to that point to negative for short,,, or check the continuity of the driver trasformer primary winding itself, or a short between its primary and secondary windings.
If all of there are ok, and still LOT doesn't works, check the supply voltage to lot. Being a 21" TV, its LOT supply voltage comes upto 125VDC or so. If it is also there, try replacing the horizontal output transistor. It also doesn't help, the Line Output Transformer you have replaced is not the exact match. Sony EHT transformers are critical in construction and in winding. Keep it in mind, and buy an another. If you need any assistance freom me, don't hesitate, ask me through Fixya. OK.
Posted on Nov 05, 2010
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Posted on Jan 02, 2017
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