ASUS UX51VZ-DH71 - Back Light SMD Fuse

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ASUS UX51VZ-DH71 - Back Light SMD Fuse

Postby Coldfuse » Sat Feb 14, 2015 9:30 pm

Model: UX51VZ-DH71
Motherboard: 60-NWOMB1A01-B07

  • Description of issue: Back light for LED Screen does not receive power.
  • What caused the issue: After fixing a no sound issue on the laptop, during reassembly, I mistakenly reconnected the battery, before reconnecting the inverter ribbon cable back to the inverter slot.
  • Notable occurrences: Corners of the inverter slot, and ports on the right sparked once. I immediately unplugged the battery, and took a break.
  • Functionality of product: Everything functions perfectly, aside from the Back Light.
  • Solution: I need help identifying the fuse, confirmation or relevant knowledge reviewed and fixed and any further information that anyone could provide. So I can then commence a chip-level repair.

  1. Data is still transmitted to inverter card, verified by shining a light into the screen, faint image then appears.
  2. The mini-VGA port on the side that sparked functions, and allows connectivity to an external monitor, which confirms the video controller is working. Everything is functioning, including the ports that sparked and test perfectly with a multimeter.
  3. Multimeter shows a fuse like object testing no continuity to the left of power supply, this could just be a capacitor, it looks identical to a fuse with no marking.
  4. Power supply can be traced (1) to the inverter slot, through capacitor -> four prong SMD fuse with O marking -> Inverter slot.
  5. The four prong object which I believe to be the SMD fuse for the inverter card power, registers .1 @ 200ohm reading and all other readings, unless I test the fuse using 1 prong per side of fuse diagonally, then registers 1.
  6. Unable to find any identifiers for the fuse, that indicate the product number of the fuse or the rating.
  7. Unable to get support or any schematics from ASUS or abroad, as of yet.
  8. I have not solder balled anything, or attempted to bypass anything in fear of further damage or incorrect knowledge.

I would greatly appreciate any support that could be provided, as my product is no longer under warranty and ASUS won't budge for any information. I can't afford to replace this specific motherboard, and I can't even find one that matches my specs or model number, I've even checked manufacture and export databases. As you can see, I have provided imagery of the board for further assistance in examining the product.

Thank you, - J.S.

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Joined: Sat Feb 14, 2015 9:24 pm

Re: ASUS UX51VZ-DH71 - Back Light SMD Fuse

Postby Karlsweldt » Sun Feb 15, 2015 6:47 am

The only proper way to find a possible fuse for that inverter board is to have the schematic. The fuse could be on the main board or on the inverter board. Typically, would be marked as an "F1" or similar. the "F" denoting fuse. But not likely a stand-alone fuse, rather a tiny surface-soldered component.
That inverter board generates 200 volts or higher, to ensure a flash over in the CCFL tube.. then drops to maybe 50~60 volts operational. With no load on that initial voltage, it can spark across tiny gaps on board traces. Or across the windings of the tiny transformer.
Would be best to replace the inverter board, if you note soot marks from sparking. Might be all that is needed.
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