Macbook A1706 EMC3071 (2017 Touchbar)

[piernov]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Usually C7081, but could be anyone on that line.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

yes, the dual diode for sure is required to be replaced. Order spares along with the regulator.

See attached. Remove both of these capacitors off the logic board.

No power to the board -> check the resistance again on D6902, pin # 3 after these caps have been removed.

We are trying to determine which part is causing this line to be loaded down so much. These caps are not polarized so they can be placed back in either direction after this quick test.

Hi,

I remove the caps and i have around 3.2kohm on pad #2 D6902.
The diode isn't on board, i lost it yesterday...
Thank you

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Can you check the resistance to ground of pin #3 of D6902?

These caps that were removed are camped onto pin #3 of this dual diode. We are attempting to confirm if any of these parts are shorted and causing the low resistance.

If the resistance is still low, locate the 3rd cap referenced above by @Piernov which I missed to mention in my list. As a quick test, remove it also and confirm the resistance to ground.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

The resistance to pin#3 is OL now. Do I desolder the other cap?

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Very good. So now we know that one of these removed caps is causing the short.

You can measure each cap while it is on your table. The low resistance cap(s) is defective.

You do not need to remove the 3rd cap. It is not the root cause of this fault.

Just replace the dual diode.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

I again tested the resistance to Pad #3 just to be sure and here I am quite surprised with the result.
In fact, the value starts at 30mohm and gradually rises to OL.
Is this normal?

Iput back the old diode to see what happen and now, i have 5.11V on pin #2 and 3.88 on pin #3.
For Pin #1, i only have 0.48V.

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Yes, it is normal. At least one of the 2 caps you have removed was defective and causing the very low resistance to ground. The low capacitance cap(s) will not be missed.

If you have a donor cap, be sure to confirm the cap can support 20V (min) since this rail will hit that voltage when it is working under normal conditions. Suggest 25v or higher, if you will be replacing the cap(s).

Next time you replace this dual diode, the diode should not self-destruct. The part was killed due to too much of a current draw for the diode rating due to the shorted cap.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

I take the latest diode from my donor board and replace it. Now I see with the USB tester that the card absorbs 0.30 - 0.50A but when measuring the diode, I no longer have the 3.8V and 5.11V...
I end up with 0.30V~ and 0.50~
On the other hand, I feel a little heat now at the level of the U3200 component, which I didn't have at all until then.
Does the card have to be placed back in the mac to find the voltages or should I find 3.8 and 5.11?

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Confirm the voltage on each pin of D6902.

Pin # 3 is the most important as it feeds this local 3v3 regulator.

Respectively, what is the voltage at the output of the coil L6900, pin # 2 ?

If you have ~5 volts or higher going into the IC @ U6903, then this regulator should output 3v3 if it is working properly.

Confirm it. This 3v3 is critical to allow many parts to power up on the logic board.

You can continue to test on the table.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Ok now, the board doesn't drain any current again...

D6902 : Pin #1 : 0.01 , Pin #2 : 5.0V, Pin #3 0V.
L6900 : 0V on both side...

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

It is possible that the cap shorting event is causing this mischief.

Remove all power, check the resistance to ground of D6902, pin # 3 again.

If the resistance is still high (not as low as original testing), then configure your meter into DIODE mode.

Red meter probe on pin # 2 = ANODE (positive side); black meter probe on pin # 3 = common CATHODE (negative side) - the meter should conduct / beep. Confirm it.

Then reverse the meter leads and the diode should block and not conduct / beep. Otherwise the diode is defective.

These dual diodes are well under $1 USD each. Always buy spares.

If the diode is behaving, then the regulator may be causing this dip to 0V.

The regulator @ U6903 may need to be replaced. Sometimes, L6900 also goes out with the party. Each are low cost parts (Aliexpress).

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Sorry, my work takes me a lot of time in this return to school after vacation, which means that I can take time to answer... I apologize.
Resistance to ground of D6902, pin # 3 again 0.009 ohm

If the resistance is still high (not as low as original testing), then configure your meter into DIODE mode.

Red meter probe on pin # 2 = ANODE (positive side); black meter probe on pin # 3 = common CATHODE (negative side) - the meter should conduct / beep. : No beep but if i put black probe on Pin #2 and red on Pin #1 : short bip (a second).

The diode was functionnal on donor board.
The previous one had burned, this one seems to have fried. I'm afraid something else is going on, isn't it? I will try to buy some but not knowing the characteristics of these diodes and the Aliexpress seller not answering me, I have not done so yet.

About U6903, is it neccessary to order a new unit ? I find 2 "versions" for the same reference : and this one : "
Which of the two is the correct one please?

Thanks again and sorry for the delay in replying...

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Yes, excessive current draw (aka too much of a load) is killing this dual diode). Order spares.

Remove all power.

Remove this dead diode and check the resistance to ground again at pin #3 to ground without this diode.

What is the reading?

The short could be the capacitor referenced earlier by @Piernov. Locate this capacitor and remove it. Check the resistance again.

U6903 may be defective. What are the topside laser markings of this component? We want the same part but the date code is not critical.

Before replacing with fresh parts, we need to eliminate the short or the diode killer. The killer could be u6903. Does it look shifty??

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

On pin #3 without diode, i have between 1 and 4 ohm, same without the C7081 cap.

I try to check in Beep mode, pin #3 : beep to the ground.

The u6903 looks good. The ref is : AAC BDC.
Thank you again

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

U6903 has to be the part that is killing the diode since it is the only one left on this common trace.

Apply flux with low air pressure so other parts do not go flying to remove u6903 and measure the resistance to ground again.

The 1-4 ohms is a short somewhere and has to be resolved.

Q: Was this laptop worked on by another shop? Is U6903 the factory original from Apple?

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

I'm going to remove the U6903 to see it but I won't be able to do it until Monday... I've just been called urgently for my child.
I'll post the result on Monday if you don't mind?
Thank you for your patience and the time you devote to me!

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Certainly. No worries. Family first.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Certainly. No worries. Family first.

Hi

So, i remove the U6903 and Pin #3 still shorted. I don't have stencil to reball it if i need to put back again.

[mon2]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

With no power, meter in resistance mode.

Post the resistance to ground measurement of this dual diode, pin # 3.

If I am following this thread correctly, you should have nothing on this pin # 3 (diode + caps + U6903 are all removed) ? So this has to be without a short now.

Post pics of this region so we can review.

[kurtspirit]

Re: Macbook A1706 EMC3071 (2017 Touchbar)

Ok, i remove the C6906 and now, i don't have any short on pin #3 of D6902.
The resistance is around 72koHm