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.

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I would suggest you check out the forums over at BadCaps.net (not sure if I'm allowed saying that here?). The members there are really into TV repairs, which most of time are capacitor related. Also, plug your TV model number over at YouTube, you might be surprised to see a solution waiting for you. Good luck.

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OK, thanks I will try that. :)

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Hi,

Here is a link to the service manual for your TV.

Scroll to section 6-8 and 6-9 to see LED blink error code meanings, hopefully it will help you to find your problem

http://elektrotanya.com/sharp_lc-60le635...

When the sentence below the Document preview box changes from This file is downloadable free of charge: ...processing to This file is downloadable free of charge: Get Manual, click on the Get Manual as this is the download link.

Update (11/25/2016)

Hi,

Looks like the CPU has +3.3V / +1.5V / +1.2V and +1.1V supplied to it.

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Thanks that Manuel is very detailed I have figured out how to get the details form the LED flashing system the thing is, the manuel sais it's a cpu problem but a guy on you tube had the same problem and changed the PSU maybe the motherboard needs 12v for CPU and stuff, I have only measured the 5v. I'll do that and post my results.

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Yes but the voltages for CPU and what I found out the PS_ON and PNL_POW switching signals for the PSU are regulated by the motherboard. The PSU outputs exactly the voltages is should 13.5V on the main rail and 5V backup voltage. PS_ON is only 2.8V, a voltage not specified on the block diagram of the mb the voltage of that signal should drive the opto-cuplers on the PSU to fully power the thing on but they are very low themselves 1.1-0.8V on the diode side, maybe because PS_ON is low too. The PNL_POW is the signal that powers on the panel and sits at a voltage of 1.randomV, it jumps around and is to low. So I'm looking for a motherboard, maybe one with broken HDMI's for testing.

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Hi, Found this which may be of interest to you in the future .

https://electro-medical.blogspot.com.au/...

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OK, thanks :)

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