Hi to all:


I have epoch making digital converter box for analog tv line 1080p multifunctional hd digital box tv converters set top box. I had the box for years that was working. The other day plug in ac outlet no display no power. This box is discontinuted from china was purchased from amazon. Yes their are other new boxes I can buy but I like to find out why it failed? This box used ac with psu in the box. I purchased a different one that used the psu outside the box and it failed in 2 days no power and no display. And sent back for replacement. At first I though amazon box got jolt from ac but then when the box went dead it used a psu that supplied 5vdc at 1.5amp. When I checked psu it was 5vdc so psu was ok. Same problem two different units! So question is what is the best way to find the short circuit on the circuit board? I stared taking components off the circuit board to try find the short circuit. I took one leg of schottky rectifier ss36 which was shorted till I removed one leg. Then tested ok. Ec3 was shorted till I removed it from board then tested ok. Without schematic this is really going to be hard to find the shorted component. Have any ideas how I should shoot this type of trouble? To give you idea what I am dealing with on this board. Here are some things board uses usb port hdmi port video and audio port and rf port. Some of components are so small you can only see with a loop. Their is also special ic chips and ram on this board. I think the system on this board only runs at 3vdc because their only ams1117 3.3 volt regulator on the board no 5vdc regulators. Theirs some of ic chips on board u20 h5ps5162gfr u2 aip650eo led driver u7 dc1916 8pin unknown u13 jwa5j unkown u9 ms81237 unknown 528 pin u4 pn8366 unknown abs bridge rectifier test ok can not check ram because of no power. Unknow large scale ic chip with heat sink on it. How add attachment for pictures of unit circuit board?

Best regards,

Ralph