[SOLVED]820-3437 - No backlight.

[gcain]

Take a look at how the top layer is bubbling.

Is this worth repairing?



Issue seems to be that BLK_PWM is at 0.460v and BLK_EN is also at 0.460v.

 

[gcain]

Better photo.

https://photos.app.goo.gl/x7v0w3X4Ezk8Kaau1

 

[aprendiz]

Yes it is fixable... Maybe need to run some wires but it has a good chance...

 

[gcain]

BKL_PWM @ C7704 with no screen cycles from 0.340 - 1v - 1.4v and back again.
Connect a screen and I get basically 0v.

I removed C7704 because it looked yuck with no change.

BKL_PWM should be around 3.4v right?

If I jump C7704::1 to 3.4v I get a backlight; so I'm onto it, just need to resolve BKL_PWM.

 

[dukefawks]

PWM can be in the 1.4-3V range. What have you done to fix? I would wipe the whole area, check traces and start fresh.

 

[gcain]

I can tell the traces are corroded out just by looking. How do I run a jumper to PWM when it comes out of CPU?

 

[dukefawks]

Remove R7704 and see what the diode mode readings are on both sides to determine if trace is really fucked.

 

[gcain]

You can mark this solved.

I ran a very short jumper wire to what was left of the test point next to R7704 and backlight with brightness works again.