A2159 820-01598 no image

[hgoncalves]

Hi,

I have an A2159 820-01598 with no image / backlight on internal display, but I have external image.

Already tried with known good display.

Client has droped a bit of coffe on it, and it has a bit of corrosion on L8420, and on U8400 area.

Several test pads under PPVOUT_S0_LCDBKLT_F caps are burnt (gone), and I only have 12V on PPVOUT_S0_LCDBKLT_F (not sure if it should that low).

BKLT_EN_R = 3.288V

BKLT_SDA/SCL = 4.5V

Can you help?

 

[2informaticos]

You should remove and resolder U8400 and other affected components.
Check all traces in that area.

 

[hgoncalves]

Hi,
I've removed U8400 and soldered again, and replaced L8420 with an 47 ohm resistor (0402), but I have the same result.

I think that on the first power on It showed the Apple logo for a sec, but then nothing else. Complete black image.

 

[2informaticos]

"replaced L8420 with an 47 ohm resistor"
That is just a coil; why did you replace it with a resistor???
47 ohm is not its resistance for DC current!
You must get 0 ohm reading in ohm scale...

 

[hgoncalves]

Hi,

I've replaced L8420 with a 47 ohm resistor, because I don't have a donor board of the same model, either a coil to replace it, and it was the spec on the schematic (I thought it will do the job).

Can I replace it with a 0 ohm resistor?

 

[2informaticos]

As I said, 47 ohm is not its resistance in DC current.
That is the resistance for AC current.
Use a tiny wire instead...

 

[hgoncalves]

The wire solved the problem.

TKS!