[Repost] Sharp LCD 46LE730E no image/sound

Hello everyone,

Trying to figure out what's wrong with my TV. I've been searching around for a while, so I'll make a repost covering what I've discover until now.

Here's the circuit (part of the power supply, which is supposed to power LED strips).

My first discovery was that instead of 60V, I measured 100VDC on label LED1A, LED3A and 60V (upper part of the image). A kind user from this sub suggested that the problem was that the 60V supply was an unregulated one, thus will be high if unloaded. From there I proceeded to disassemble the panel and tested LEDs one by one (painful process). Everything was working fine, I also tested cables and the connector for discontinuity. I suppose the problem comes from elsewhere.

So back to the circuit, I try now to discover what's wrong.

On the circuit you can see U901 (datasheet), this is a dual channel PWM driver for boost converter, to provide sufficient voltage for the LED strips.

Here are my observations :

• Tested fuse FB901, 902, 903, 904.

• BL_ON is suppose to activate U901, the signal looks like this. I expected to be a flat 5V to power on at all time (Vcc for U901). Edit : I've looked at the collector from Q910, there's a signal similar from BL_ON but we never see 12VDC..

• U901 outputs : 1 & 2.

• Q901 & Q902, two NMOSFET for the boost converters are in fact never activated (there's always 100VDC on their drain). I expected them to oscillate between 60V and 0V for the boost to be working.

• U902 looks like it was overheating. Edit : Scoped it.

I'll keep searching and edit the main post to add observations as I'm looking for clues.

Thank you.