MacBook Pro 15" Late 2013 no chime or boot but green light on charger

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

The measurements look good, so far.

Voltage at test point # 4 ?

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Very strange. After re-test, pin 2 showing 1.5V rather than 3.3V.

Pin 4 showing 3.3V.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

But mon2, I note at C7850 pin 1, only showing 0.4V and seems to be oscillating a lot on my multimeter. Could this cap be bad?

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Could this cap be bad?

I think there is a broken trace on pin #1 of this cap. After the check below, check the resistance to ground of pin #1 of this cap. Then if the resistance is measured low, consider to remove this cap as a test.

C7850 pin 1, only showing 0.4V

This means that you do not have a solid connection on C7850, pin #1 to PP3V3_S5. Perhaps due to liquid damage.

Remove all power.

Meter in resistance mode -> check the resistance from C7850, pin #1 to pin #1 of U7810.

This resistance should be ~0 ohms.

Then apply power and confirm that pin #1 of U7810 is indeed +3v3. This is the same voltage that should be present on C7850, pin #1 but C7850 is not critical to the operation. However, very important point is that we do not know how the PCB traces have been laid out. That is, if C7850 pin #1 does not receive the +3v3 then what other components on the logic board have lost out on the same missing rail.

Check the above. You may need to take a solid piece of wire (we use wire-wrap wire - dating myself with this term) but C7850, pin #1 should be a stable +3v3 fed from PP3V3_S5.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Hi mon2, is showing 1 . even on 2M mode, for resistance.

Pin 1 on U7810 getting 3.3V, just measured it again.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Pin 1 of the cap is showing 100 to ground when using 200 mode.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Hi mon2, I removed the cap C8750.

I tested again resistance from pad 1 on U7810 to pad 1 for where C7850 was. Still showing 1 . even in 2M mode.

I then tested resistance from pad 4 on U7810 to pad 1 where C8750 was, showing very low, 01.5 on 200 mode.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

These are both pins for PP3V3_S5, something wrong with chip itself?

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

And I re-tested now pad 1 on U7810 to pad 1 where C7850, now showing 01.5 on 200 mode. Hard to probe as so small!

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

With cap removed, pin 3 now showing 1.34V, was 0.58V before. I think is still too low, should be 1.5V?

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

I tested again resistance from pad 1 on U7810 to pad 1 for where C7850 was. Still showing 1 . even in 2M mode.

This is OK as the meter is reporting that the resistance is greater than the 2M scale and this is acceptable. This confirms there is no short to ground for the pin # 1 PCB PAD (since the cap is removed).

To save on cost, multimeter manufacturers (most) will use a fixed LCD display that usually has a few fixed graphics and digits for the display. They are made dirt cheap in volume. For this reason, the '1' is used to denote that the scale being used is under the value you are measuring.

In this case, the resistance is higher than the 2M scale so '1' is displayed.

Check the resistance to ground of pin # 4 of U7810 - what is the reading ?

Now that the cap is removed, you can check the cap out of circuit with the resistance check across the 2 pins of the floating cap.

I then tested resistance from pad 4 on U7810 to pad 1 where C8750 was, showing very low, 01.5 on 200 mode.

Good. So this confirms that the trace is ok and is reaching the pad # 1 of the cap you have removed.

Now power up (without the cap) -> what is the voltage on the pad #1 of C7850 ? The voltage reading must match the same voltage as pin # 4 & # 1 of U7810.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Pad 1 showing 3.32V. Same as pin #1 and pin #4 of U7810.

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

I note at C7850 pin 1, only showing 0.4V

So now that the cap is removed, the voltage is OK @ C7850 ?

That is weird since if the voltage was 0.4v @ C7850, pin #1 then this should have impacted the same rail on other pins. They are all on the same PCB trace.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Yes voltage okay on pin 1. Cap is still removed.

System still will not boot. Can you help?

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

What is the voltage @ L7870, pin # 2 ? This should be PP1V5 as the regulator is being enabled through pin # 2 of U7810.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Showing 0.07 on 20V mode for pin #2 on L7870.

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

Remove all power. Check the resistance of R7880 and R7881. Post the readings.

Confirm the FB trace of u7810 is reaching the middle of the two resistors. Use resistance mode and no power to the logic board.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

R7880 on pin 1: 04.2 on 200k mode
R7881 on pin 1: 99.5 on 200k mode

These are both measured to ground.

How do I confirm the FB trace of u7810 is reaching the middle of the two resistors please?

[mon2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

No. Use the meter leads to check the resistance across each resistor. We want to be sure that the resistance is the same as shown in the schematic for each part.

Post the readings.

[Gigabit2]

Re: MacBook Pro 15" Late 2013 no chime or boot but green light on charger

R7880: 113.6 on 200k mode
R7881: 99.6 on 200k mode