LA-8554P No backlight

[pc1staid]

Hello fellow techs...
I have a HP Spectre XT come in for no display.
Diags have shown there is no backlight, connected to a monitor- OK, checked cabling- OK, removed screen and shone a torch through- display evident, changed screen as I have seen on a few forums, it could be the screen itself- display evident. Just no backlight.
I have managed to find a schematic for the board but I am unable to find where the backlight fuse is.
Would anyone have an idea as to where it may be located please?
Thanks in advance.

[emestee]

Re: LA-8554P No backlight

Why do you assume it's the fuse?

https://cdn.badcaps-static.com/pdfs/...5f57ec8880.pdf

This board should have similar layout. See sheet 33 for backlight control.

[pc1staid]

Re: LA-8554P No backlight

Thank you @emestee. I am using this schematic (attached) page 24.
I was refering to where it was located on the mainboard.

Schematic moved to new thread - https://www.badcaps.net/forum/showthread.php?t=124843

.

[arber1232]

Re: LA-8554P No backlight

Hello fellow techs...
I have a HP Spectre XT come in for no display.
Diags have shown there is no backlight, connected to a monitor- OK, checked cabling- OK, removed screen and shone a torch through- display evident, changed screen as I have seen on a few forums, it could be the screen itself- display evident. Just no backlight.
I have managed to find a schematic for the board but I am unable to find where the backlight fuse is.
Would anyone have an idea as to where it may be located please?
Thanks in advance.

[pc1staid]

Re: LA-8554P No backlight

thanks arber1232. The board has very little screen print on it and I have tried to pinpoint the location of where the feed comes from on the board I have been unsuccessful. I am getting no 19v at Pins 1&2. I need to find either the fuse or where if comes from on the board.

[emestee]

Re: LA-8554P No backlight

thanks arber1232. The board has very little screen print on it and I have tried to pinpoint the location of where the feed comes from on the board I have been unsuccessful. I am getting no 19v at Pins 1&2. I need to find either the fuse or where if comes from on the board.

On sheet 24 of your schematics in the upper left there's the power control scheme. You would be looking for 3 transistors not far from the LED connector. Two of them are 8-legged, and the last one would have a thick leg on top and three thin ones at the bottom.

[pc1staid]

Re: LA-8554P No backlight

On sheet 24 of your schematics in the upper left there's the power control scheme. You would be looking for 3 transistors not far from the LED connector. Two of them are 8-legged, and the last one would have a thick leg on top and three thin ones at the bottom.

Now thats what I thought, yet i couldnt find them. I was looking for 3 components and I was hopeing a fuse...

I have found what I beleive to be Q6 and Q7. No Q6a/b and its a 6 legger, Q7 is a 3 legger. looking at the schematic Q6a/b looks like 2 components were as on the board its a single component, a dual channel diode. so I think thats what was throwing me.

Thanks emestee, you have pointed me where i need to be. I will post back if i need and further assistance.