820-00165-A A1466 No image

[CraigR]

Got a bit of a odd one. A1466 Press power and I hear the chime and the screen change shades of black. (with room light off it's the backlight) I shine a light through the back and nothing on screen no logo or anything. OK I shut it down and hooked an external monitor to it then started up again and screen is normal image but nothing on external monitor. I can unhook monitor and the screen stays on just fine BUT reboot and no video again. I can repeat the process to get the screen on but what would cause this?????
Forgot to mention that I checked both sides of board for corrosion and anything out of the normal and was the cleanest board I ever seen, looked brand new no signs of anything. Also tried a PRAM and SMC reset and did nothing.

 

[2informaticos]

Post SMC_LID signal level.
Be sure to use original Magsafe 2 charger.

 

[CraigR]

3.42v

 

[2informaticos]

Original Magsafe 2 charger?
Did you check SMC_LID signal when internal LCD doesn't have image?
Also check DP_INT_HPD at same time.

 

[CraigR]

Yes, used charger and on battery. And yes checked SMC_LID with laptop running with No mage. I will need to check DP_INT_HPD and report back. Thank you for the help.

 

[CraigR]

OK, 2.45v at DP_INT_HPD but I went and checked SMC_LID right after and 0v now, then suddenly comes back to 3.4v but still nothing on screen. Checked this a few times now and same result. (Head scratcher)

 

[2informaticos]

There should be some history fault, even no liquid sign visible.
What said the client?

Post voltage at pins 3/4 and 18/19 of J8300, when there is no image.
Did you try another LCD assembly?
Even cracked, just for test.

 

[CraigR]

Bought through Auction so doing for myself. No other screen to test with. 3/4= 24.5v and 18/19= 3.28v

 

[2informaticos]

You should discard LCD first...

 

[CraigR]

Not going to toss a screen when I seen it working just fine. Makes no sense. Is there a chip that controls when to switch between external screen and onboard screen? Also did you see when I said at one time I got zero volts at SMC_LID? Other than the screen what is your best guess?

 

[2informaticos]

If SMC_LID is 0V, image and backlight both are disabled.
But you said the problem appears even with correct SMC_LID signal.
Check for internal video only with MLB and LCD connected; unplug LIO flex, TP, airport and SSD.

 

[CraigR]

Please be patient with me as I'm a bit new at this stuff and almost all my repairs have been water damage or rework from other shops.
I have the wireless card out and the SSD out and the flex cable that goes over the fan off but not sure on what the TP is? With those 3 things off I have backlight but no video again.

 

[2informaticos]

TP=TrackPad.

So now you get backlight without image on internal LCD?
This is really strange; please check for image with a flashlight.

 

[CraigR]

Oh ok, I knew it wasn't toilet paper LOL. I always did get a backlight and no image. Sorry if my first post was not clear.

 

[2informaticos]

I still recommend to try another LCD assembly.
Looks like communication problem between PCH and LCD.
If backlight is on, PCH recognizes LCD, but something goes wrong on eDP bus...

 

[CraigR]

Well 2informaticoc I guess you are correct! I got in another A1466 in this week and did a quick swap of the logic boards and screen still did not have an image unless I put on an external monitor. I put the guts in the other one and screen worked as it should. Really weird to me how that works. So any good forums to buy used Mac parts??? LOL

 

[2informaticos]

You can get good parts on Aliexpress.
Look customers reviews when you search for products...

 

[CraigR]

Yep, been getting stuff there for a long time.