Hello friend .... greetings .... the first thing ........... in samsung the sources always turn on without the need for a main ..... connect only the source with the led ... yes It turns on and does not blink the LEDs. Look well, it means that the source is working well .... Anyway, look at the voltages if they are correct ... Then continue to verify the main tries to find shorts ... They should give you the guarantee ... but if you already uncovered it, it was lost ... if it is not the video chip in the main, you should have a DC dc converter shortly, check montage capacitors in each sub-source ... if you do not try to find out the main card in some repository and that they give you guarantee .... and see if it turns out and give a price to the customer .... greetings and good luck ...