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Sharp TV 21" screen with a switch mode power supply.

Plse help as i have a power transistor(2sc5299) as switch connecting to the primary of an auto transformer and being driven by another transistor ( c3807 ) also being fed by another transistor (2sb 764)..... thus diag below
optical coupler N502 ----> B764(AF Driver) ----> C3807(hi-gain amp switch) ----> 2sc5299 ( large transistor switch ) connecting to the auto transformer.

Problem ..... the fuse keeps blowing and when checked i found that the
2sc5299 and the c3807 were gone( faulty) i checked the doides(rectifiers) and all are good. Plse explani why fuse and both transistors were blown as i have found replacement but no schema to this TV. Thanks for your prompt response as i await your findings. I have to complete this task. and i need your help ..... brgds Davies

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I have a tv receiver with a problem of no power going to the whole system thiis transistor c3807 and connected to bigger transistor c4458 are gone together with connecting diodes.any solution please?

Posted on Jul 30, 2009

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I have the same problem i need help with The values of resistors R517 + R523 + R515

Posted on Apr 28, 2010

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Dear friend i read your problm i think the transtr c5299 you fixed that not original becouse you can fix the following trstrs bu 508af,d2498,bu2520,c4460,d5148etc... some times c3807 is not orginal,you use,d882,c2229,c2482,after these things the same is repeat you must have to change disc capacitors on base and collector of c3807,

Posted on Sep 30, 2009

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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.
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