TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

[Boyxba]

I have a toshiba laptop satelite series c55-a-1h9 with a burnt item on pcb motherboard which is responsible for backlight display. the short came after installation of cable lvds and broken the leg with the v+ of backlight and made this short . the lvds cable replaced and i have working display now but not backlight. the problem is i dont know what was the component that burned in order to change it. voltage i have in this points of burned item at up side 19v and dropping and from down i have steady 19v . can anyone help me? i shall post some photos to see.

[Boyxba]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

i have seen on board view that the component is L4501 DESCRIPTION VX_L0603_H37_SMALL And has 2 contacts 1 ac-inv 2 +ac bat sys

can anyone tell me what component is this ?

[mcplslg123]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

Thats a coil in 0603 size. Do measure the resistance to GND on both pads of this coil before soldering a new coil. One of the pads may be shorted.

[Boyxba]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

Thats a coil in 0603 size. Do measure the resistance to GND on both pads of this coil before soldering a new coil. One of the pads may be shorted.

the think is that coil has burned and no component was there.... Any kind of contuctor can be replaced or must be exact the same?

[mon2]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

As per suggestion in post #3, remove all power. Meter in resistance mode. Measure the resistance to ground of each pad of this missing and burnt part.

More suggestions are:

1) replace with any 0603 size ferrite bead with high enough current support to power this lcd backlight. Recommend at least 1A-3A to be safe. For example, see MaxEcho in Taiwan for ideas. The values are not critical.

2) a better option is to place a resettable smd 0603 fuse here so this event does not repeat in the future. The fuse will stop a high current event and self-heal after the event is removed.

3) if really in a pinch and 100% sure there is shorting fault on these 2 pads or the display then you can just apply a short across these 2 pads. Note that this can lead to more damage if the fault is not fixed.

Summary, some event caused the missing part to act like a fuse and was destroyed. Likely the magnet wire of the coil heated up and was burnt from the excessive current draw.

[Boyxba]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

As per suggestion in post #3, remove all power. Meter in resistance mode. Measure the resistance to ground of each pad of this missing and burnt part.

More suggestions are:

1) replace with any 0603 size ferrite bead with high enough current support to power this lcd backlight. Recommend at least 1A-3A to be safe. For example, see MaxEcho in Taiwan for ideas. The values are not critical.

2) a better option is to place a resettable smd 0603 fuse here so this event does not repeat in the future. The fuse will stop a high current event and self-heal after the event is removed.

3) if really in a pinch and 100% sure there is shorting fault on these 2 pads or the display then you can just apply a short across these 2 pads. Note that this can lead to more damage if the fault is not fixed.

Summary, some event caused the missing part to act like a fuse and was destroyed. Likely the magnet wire of the coil heated up and was burnt from the excessive current draw.

as I mentioned before the reason that burned conductor coil was a short of 40 pin with the ground from lvds cable.. Thas why the backlight of display does not work.. A friend of mine in his action to replace the display due to dark spots he broke the small corner of lvds cable whish does not seeing with eyes and he made short to ground... After I replece the lvds cable I have picture but not backlight... Shall I leave it in this condition or I shall have more problems if I but a conductor...

[Boyxba]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

As per suggestion in post #3, remove all power. Meter in resistance mode. Measure the resistance to ground of each pad of this missing and burnt part.

More suggestions are:

1) replace with any 0603 size ferrite bead with high enough current support to power this lcd backlight. Recommend at least 1A-3A to be safe. For example, see MaxEcho in Taiwan for ideas. The values are not critical.

2) a better option is to place a resettable smd 0603 fuse here so this event does not repeat in the future. The fuse will stop a high current event and self-heal after the event is removed.

3) if really in a pinch and 100% sure there is shorting fault on these 2 pads or the display then you can just apply a short across these 2 pads. Note that this can lead to more damage if the fault is not fixed.

Summary, some event caused the missing part to act like a fuse and was destroyed. Likely the magnet wire of the coil heated up and was burnt from the excessive current draw.

I put a conductor but makes short circuit and does not start the laptop after removing it it works without backlight and the port of vga works fine.. On 40 pin of lvds has 3.3v...can I make backlight to work without taking signal from motherboard

[mon2]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

Then this coil is not a filter coil for EMI but rather for a switching power supply and a replacement coil will be required.

Trace this part to the nearby IC which will be the power rail switching controller. Post a clear pic and/or topside markings for a review. Ideally we can identify the switching power controller and then locate a datasheet to learn more about this missing inductor.

[Boyxba]

Re: TOSHIBA BACKLIGHT MAINBOARD C55-a-1h9

I put a conductor but makes short circuit and does not start the laptop after removing it it works without backlight and the port of vga works fine.. On 40 pin of lvds has 3.3v...can I make backlight to work without taking signal from motherboard

Finnaly I put a jumper on contacts and all work fine...