How can I fix the LED driver chips of a TV PSU?
Hello, I recently got a 60" LED Sharp TV. The problem is that every time I power it on it will just switch on the power LED and try to powerup 3 times (LED stays on for long switches off and then on again) after that it will flash the LED 3 times pause and flash 3 times again until I pull the plug. I opened the thing and took out the PSU, witch on this TV is a LED backlight circuit / PSU combo. Btw. I have also looked at the panel with a powerful touch to see if anything is displayed but its not. I have checked all caps, mosfets (main supply), optocuplers and diodes for defects all are working perfectly fine. I measured the voltages to the LED mosfets (63v) and the 5v to the mainboard. The only problem i could find was that the mosfets that should switch the power to the backlight don't let the voltage through. No voltage on gate and output 63 on source. The 4 parallel fets are controlled by 4 BD9285F ics underneath (http://rohmfs.rohm.com/en/products/datab...). I have checked vcc and uvlo (4.7v) these things are new to me so I don't relay understand why they don't let the voltage through. It could be a protection feature but the mosfts look fine (haven't desoldered them yet but they all read the same) and they don't even try to power the mosfets tried to capture the voltage but nope. I don't get it :( , does anyone have an idea how these ic's opperate and what the problem could be?
Man, things where much easer in the old days :D.
Is this a good question?