820-00138-A turns on but no Display

[mferna14]

Today I am working on a MacBook Pro (Retina, 15-inch, Mid 2015) MB 820-00138-A. It turns on fine but no Display. I checked with a known good LCD panel but still no display. Checked voltages on U7701, it's getting the 5v on pin 5 & 18, but BKLT_EN_R pin 17 reads 0V where as this is an enable pin, should I not get 3.3v on this pin?? PPBUS_SW_LCDBKLT_PWR I get 12.38V & LCDBKLT_EN_L 12.45V. Why BKLT_EN_R pin 17 reads 0V, zero ohms resistor is ok. Any help would be greatly appreciated. Thanks

[mferna14]

Re: 820-00138-A turns on but no Display

Can anyone help me in this repairs. I am just stuck. I would appreciate your help. Thanks

[piernov]

Re: 820-00138-A turns on but no Display

Image must be present before worrying about backlight as always.

[mferna14]

Re: 820-00138-A turns on but no Display

Thank for the answer "piernov". Please inform me then what is the first step to take, I would appreciate. Thanks

[mferna14]

Re: 820-00138-A turns on but no Display

I check all the require voltages & all are present. The CPU turn warm too, but no display. Does this board have a Video chip or its embedded in the CPU or elsewhere???

[mon2]

Re: 820-00138-A turns on but no Display

Is this a backlight issue or a video card / interface fault?

Use a flashlight on the front / sides to see if you can view any of the screen graphics when box is on. If yes, then it is a backlight issue. Otherwise you have video card / connector / cable issues to review.

[mferna14]

Re: 820-00138-A turns on but no Display

I checked with a 100% Known good LCD screen. LCD screen is not the issue. "Video Card", I think you mean video chip, this is why I was a bit confused, does this board have the video chip embedded into a chip or what??

[mferna14]

Re: 820-00138-A turns on but no Display

Any more help please!!!