VPCCA290X (MBX-239) No backlight in LED screen

[orientalsniper]

Hello all, I've tested most fuses and they apparently have good reading (0.2-0.6 ohms). Also I desoldered Fuse F15 and just used solder to bridge it, yet no LED screens I've tried on (about 10 screens) have the backlight on, yet they work in another laptop.

It works externally and I can also detect a change when I turn the laptop on. Help please?

[scsblackdragon]

Re: VPCCA290X (MBX-239) No backlight in LED screen

is there a voltage present at the fuse near the lcd connector?

[spidey]

Re: VPCCA290X (MBX-239) No backlight in LED screen

unfortunately there is no shcematic for your board. What you can do is find a similar one and trace back backlight voltages.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

I'm getting 0V at F15 (it's a very small brownish fuse with an N marking). Getting 0.008V at F13 (K marking). There's no fuse close to LCD connector, F15 is pretty close under the connector though.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

Hello again, I measured LVC08A, which I think is the LED driver, on VCC (Pin14) getting 3.3V. Any suggestion on what else to check?

[dj_ricoh]

Re: VPCCA290X (MBX-239) No backlight in LED screen

why did you not post some macro pics?

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

Sorry! Coming right up!

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

Here you go, check attachment.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

I think this one looks better.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

So I was measuring voltages to everything around that fuse and everything had a reading except that big capacitor (C809), besides finding a similar one (how can I tell besides the sizing?), how can I test that capacitor? It's seems to be a 4520.

[dspok]

Re: VPCCA290X (MBX-239) No backlight in LED screen

@orientalsniper
100% problem is with the blacklight fuse. check fuse with "N" "Z" mark if they have voltages in both points.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

F15 was an N, it has solder bridge now, however I don't get any voltage reading in F15, I think it has to do with that big capacitor close to it (C809), it has no voltage readings either. But I don't know how else to test it.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

I can confirm 100% it's the Fuse F15, I checked continuity with solder bridge in Fuse with the last 3 pins of the LVDS connector. Does anyone have any idea how is the fuse being fed? I'm trying to trace back with continuity, will report back.

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

Major ooops... I was testing F15 with both probes in it, now that I'm testing it with a ground I'm getting 18V, would this mean the fault could be in the LVDS cable?

[rtstorm]

Re: VPCCA290X (MBX-239) No backlight in LED screen

disassamble LCD screen and check if there is 19V on LED connector when turn on laptop

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

Hello, what are the relevant pins for the backlight?

I tested the last 3 pins and they have 19.03V.

[rtstorm]

Re: VPCCA290X (MBX-239) No backlight in LED screen

did you have something like these??

[trebo]

Re: VPCCA290X (MBX-239) No backlight in LED screen

Major ooops... I was testing F15 with both probes in it, now that I'm testing it with a ground I'm getting 18V, would this mean the fault could be in the LVDS cable?

yes, swap it if you can, nothing to loose, eliminate it

[orientalsniper]

Re: VPCCA290X (MBX-239) No backlight in LED screen

@trebo: that cable is so expensive! I will order it as last resort.

@rtstorm: Last 2 pins of the connector has 19V.

[rtstorm]

Re: VPCCA290X (MBX-239) No backlight in LED screen

i think your LED backlight is dead, because you have 19V on it and no background light. I did not understand did you have a picture when you light flashlight in LCD?