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

I think the labels should be reversed?

[Gigabit2]

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

I just checked and these are the ratings, labels are correct.

[mon2]

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

According to the schematic, the 100k resistor should be connected to the coil (inductor).

Have these resistors been changed?

Confirm the locations for each again.

[Gigabit2]

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

I have flipped the resistors now with my rework station so they match the schematic.

Still seeing the same readings 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

Apply plenty of flux and consider to reflow u7810.

Allow for time and heat to make this part swim into place on the PCB pads. Be patient to prevent damage.

Then with tweezers, when the solder is in liquid state, use a very gentle tap in a corner of u7810. The chip will naturally push away and as you let go of the tweezers, the chip will bounce back and settle onto the pcb pads.

Louis calls this 'make it dance' move.

With patience, the part will be soldered correctly. Otherwise can lead to permanent damage of the pads.

Also, confirm that the ic was properly seated on the pcb with respect to pin #1 = pin #1 on the chip.

[Gigabit2]

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

I completed reflow. Image is here:



It looks aligned to me.

[Gigabit2]

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

I lost R7881, I will source a replacement.

Nonetheless, PPV15_S0 remains low, 0.05 on 20V mode

[mon2]

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

Both resistors MUST be present. Never power up till they are present. The FB = feedback voltage that is defined by these 2 resistors. Respectively, the output rail can overshoot and permanently kill all downstream parts using this rail with the wrong or missing resistors. This is typical of most switching power supply chips that are adjustable.

The formula on the schematic shows how the resistors affect the output voltage rail value.

Some have these settings internal to the device.

[Gigabit2]

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

Thanks mon2.

I will source replacement resistor and not power on until then.

Can you comment on how reflow looks?

[mon2]

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

The alignment looks good but the main concern is if the bottom side 'metal belly' of the IC is mating with the PCB.

This was the #1 issue on an audio IC (XMOS, UK) when we reviewed many many OEM designs in the forum. Most of the PCBA faults where due to this metal belly being not soldered and JTAG programming would fail.

This is only a precaution but suggest that using low air pressure (move the hot air nozzle in circles over the IC) + high heat and use tweezers to push down this IC to be sure the metal belly is soldered. Do not shift the IC but just pushing down to guarantee the belly is kissing the PCB surface.

You may be already ok so consider to use IPA to clean up the flux residue with a Q-tip. Then wait for the replacement resistor to arrive.

[Gigabit2]

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

Hi mon2,

I ordered a new IC as well just in case but the resistor should arrive tomorrow.

I must get a new hot air station. Mine is Chinese clone and temp has to be high for a long time. Worried about damage

[mon2]

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

We purchased the following brand:

https://www.aliexpress.com/item/1005...martRedirect=y

It is by BEST Tools and is a clone of some other brand. Have met them at past electronic trade fairs in HK that we have attended for the past ~15-20 years. They have stated that we can purchase spare parts if the unit ever needs repair. So far, very pleased with the unit. One of these days, will read the manual about the assorted features / timers onboard. Came across one case where a pre-heater (underside) was mandatory - Asus motherboard. Could not budge the SMD 8 pin flash IC. We then purchased the HAKKO (true, not clone) version of the heater from Ebay (had the digikey sticker on the box; surplus but new for some shop in the USA).

This tool can dial upto 550C. No complaints but some PCBs can change and darken in color for the green solder mask (ie. burn?) if you leave it on too long on the max temp. There are others on the market and this one varies a bit on the prices from shop to shop.

It is a clone of the 'Quick' brand:

https://www.youtube.com/watch?v=iq2Umu4P-Ts

[Gigabit2]

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

Hi mon2,

Was still seeing same results after replacing resistor.

I have removed IC and I think issue is these missing pads:



Can this be salvaged? I will also order a new IC as old one had small micro fractures I saw under microscope.

[mon2]

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

Check with a meter in resistance mode of the wounded pads and see if the pad is able to make a contact by following the PCB trace. If there is enough meat left, then yes, it can be saved.

Also, sometimes, such parts like this one (DFN package) have some meat on the VERTICAL rise of the IC that can be used to repair the contact.

Always use lots of flux and enough heat to allow for the part to swim in the liquid solder - use a gentle nudge of the tweezers to see if the temp has been reached. Never rush the process. If needed, use an underside preheater.

BTW - see a disturbed SMD cap south of the large coil on the right side.

[Gigabit2]

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

Hi mon2,

Pin 6 not making good continuity at all. I want to scratch some copper of to try and check trace but do you know a good tool for this? Where is the trace going?



As this is coming out of chip, I think I can repair with wire + new pad, do you think this is best approach?

Pin 4 is okay, I checked continuity and is looking ok.

Pin 2 seems intermittent, do you know where this trace goes?

So it looks like all IN pins okay, just out that is issue, which makes sense I think. We were seeing low/no voltage out before when IC connected