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Laptop Screen Backlight Fuse (Dell Inspiron 7559): is this the right one?

Merudo

New Member
I'm trying to find a broken fuse for a Dell Inspiron 7559 laptop.

I'm not sure if I've located it or if it's a fuse for something else. How can I tell?

Here's a picture of what I found. (it's the "F" fuse next to FS1)
 

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rjenkinsgb

Well-Known Member
Most Helpful Member
FS1 is possibly a "Polyswitch" style solid state fuse, a PTC resistor. They have that case style with the notched ends.
Does it read as a low value when you test it with a multimeter? It should be low ohms (single digits) or fractions of an ohm.
That style is normally self-resetting, they go back to normal when the overload is removed.

Some laptops do have a conventional miniature wire fuse in the power input circuit. The ones I've seen in that application look like a miniature axial resistor.

Some examples of miniature fuse styles:
https://uk.rs-online.com/web/c/fuses-sockets-circuit-breakers/fuses-pcb/non-resettable-wire-ended-fuses/?applied-dimensions=4294853422,4294584567


Edit - just searched the computer model and found it has an option for a backlit keyboard.
The legend near the connector in your photo implies that's what those components are for.

If the problem is the screen backlight, you need to look near where the screen connections are on the main board.

- Found another post re. the backlight problem, apparently one cause is a failure of a mosfet, Q7.

See the "Best solution" post in this thread; it also has a link to a schematic.
 
Last edited:

ARROW ARK

New Member
I'm trying to find a broken fuse for a Dell Inspiron 7559 laptop.

I'm not sure if I've located it or if it's a fuse for something else. How can I tell?

Here's a picture of what I found. (it's the "F" fuse next to FS1)

Greetings Merudo, my laptop dell inspiron 15 7559 it happened the same as yours, I saw your comments on this page and another, but even with that I could not resolve, because I do not know what the MOSFET transistor exactly on the motherboard , if you have some images available and some way to guide what I should do, I would thank you brother.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Oops... It looks like I forgot to paste in the forum link, though you have already found the same thread!

Here is the reference: https://forums.tomsguide.com/threads/lcd-backlight-not-powered-dell-inspiron-7559.441134/
And this is the download link for the schematic, from that thread: http://s000.tinyupload.com/?file_id=02860262227962922751

Q7 in the diagram is on page 57 of that schematic, in a block labelled "brightness power".

I can't find a clear enough photo of a motherboard to identify individual components, but the LCD connector looks to be clearly labelled on the motherboard. Q7 is quite possibly somewhere near that connector, as it feeds power directly to the last four pins of the LCD connector (at the opposite end to any pin 1 ID marking against the connector).

If you still cannot find it, can you take some good photos so the component identification is clearly readable? Someone on here may then be able to spot something.
 

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