Apple macbookpro 13" A1708 2017

[Fabbrone]

Hello everyone, I have this macbookpro 13 2017 a1408 that turning it on does not hear the (boing) and does not display anything. But by connecting an external video you can see it perfectly. Could it be a screen or mainboard problem?

[SMDFlea]

Re: Apple macbookpro 13" A1708 2017

tried a PRAM reset

[Fabbrone]

Re: Apple macbookpro 13" A1708 2017

I have already tried Option, Command, P and R for 20 seconds but nothing

[ktmmotocross]

Re: Apple macbookpro 13" A1708 2017

did u not hear about flexgate?

search for service recalls

[Fabbrone]

Re: Apple macbookpro 13" A1708 2017

yes I contacted apple but they assert that the years concerned are only those of 2016!

[mon2]

Re: Apple macbookpro 13" A1708 2017

If you apply a flashlight on the display, can you see any of the screen graphics? Try from front side at various angles.

Flexgate was common to more than 2016 models.

We had to replace the full display assembly to fix a client's a1707 with similar issues. The display however would come and go at a certain angle of the lid opening. After replacing the display assembly, worked fine. Client just wanted it working and said he would challenge Apple on his own.

For your unit, do you see video every time on the external display?

Any liquid damage to the logic board?

Post the backlight voltage for the lcd display with the lid open.

Also see here:

https://www.ifixit.com/Answers/View/...6+no+backlight

[piernov]

Re: Apple macbookpro 13" A1708 2017

A1708 2016 and 2017 are the exact same machine (apart from the newer CPU) so of course they have the same defect. It's just a scam from Apple. (A1707 is also affected but not covered either, and newer models are a bit more reliable but the issue is still there)
If you go to Apple Store or AASP and insist a bit they may accept to repair it for free as well.
That's of course if it is indeed a flexgate issue. If it is liquid damage or physical damage that won't work.

[Fabbrone]

Re: Apple macbookpro 13" A1708 2017

The mac disassembling it is very clean it does not seem to have worked so much, every time I turn it on you can see it on an external monitor and by properly lighting the video you see the screen. How can I check the backlight voltage?

[mon2]

Re: Apple macbookpro 13" A1708 2017

If you CAN see the LCD display (on the macbook) with a flashlight / phone, etc. light then your backlight is defective.

This is a boost regulator that takes in a low voltage and multiplies the voltage (boost) to 25-45 volts for the LEDs that are behind the LCD display. Once this voltage rail is working, you can see the display.

The question now is if the backlight voltage is defective or working ok at the logic board level but due to flexgate (ie. broken cables to the display assembly) not reaching the led matrix of the display assembly.

Can you post the 820-xxxx logic board number for your macbook pro ?

If not known, will try to locate it another way. Once we have the details, using the boardview file viewer, we can locate the backlight voltage rail for your inspection.

You will need a multimeter in voltage mode setting.

Would you have this tool ? If not, you should be able to at least arm yourself with enough info to take it to a local repair shop. Often Apple likes to use the TI LP8550 LED driver IC which is around $3 USD each + labor to install the part.

https://www.ti.com/product/LP8550?ke...rch-everything

Let me check some schematics to confirm...

Ok, it is a different part from TI - see attached for the 2 logic boards used by Apple for the A1708.

Have a look at the PCB shape - which shape is your logic board ?

[Fabbrone]

Re: Apple macbookpro 13" A1708 2017

Ok I have a multimeter available and the main board is 820-00840-01

[mon2]

Re: Apple macbookpro 13" A1708 2017

Check and review the voltage @ L8410, pin # 2.

Be very careful on the powering of the logic board and keep away from all metal objects during this review. Must not short circuit out to anything else on your work table.

This inductor (coil @ L8410 may be on the bottom side of your logic board).

With your meter in volts mode, black meter probe to ground -> red meter probe to pin # 2 of L8410.

Post your readings.

Update - you can probe the backlight voltage on the TOPSIDE

See revised last pix.

[Fabbrone]

Re: Apple macbookpro 13" A1708 2017

There are 11.68V

[mon2]

Re: Apple macbookpro 13" A1708 2017

There are 11.68V

The backlight is not working. This rail should be much higher in voltage.

[ktmmotocross]

Re: Apple macbookpro 13" A1708 2017

not need to check have two of them with same backlight issue. when u check backlight flex u will see there is crack on it. bad apple design. as repair their make longer flex that not bend/crack

[mon2]

Re: Apple macbookpro 13" A1708 2017

@ktmmotocross, I think OP is saying the backlight voltage on the logic board is @ 11.68V for the LED driver.

Does the LED driver require the LCD display mated to generate this backlight voltage ?

Unless I am mistaken (could be), the logic board should generate the backlight at a much higher voltage even with the LCD not connected. It is just a boost power supply but not sure if this boost power supply is enabled over I2C / SMBUS interface ONLY after the LCD is detected.

I think if U8400 (Pin 17 = EN) is HIGH, then the LCD backlight should be much higher in value.

[piernov]

Re: Apple macbookpro 13" A1708 2017

Backlight won't be enabled with no LCD connected.

[Fabbrone]

Re: Apple macbookpro 13" A1708 2017

thanks for the support, i gave back to the owner telling him to insist with apple