Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

[afarr]

Hi all, this is my first post, I offered to check out a friends MacBook Pro, A1706 which doesn't power on, before this happened they smelt something burning inside, and Apple refused to help with out being out of warranty.

Among investigating a capacitor on the logic board spilt and scorched surrounding area please refer to images; https://imgur.com/a/AmSwFr3

I found a schematic (x362 MLB Schematic) for the logic board on a thread from this site, I'm unsure about the right terminology when describing so please forgive me.

On the location I assume is the blown capacitor, C7490 which is the IMVP power block and why the laptop doesn't power at all.

Please refer to this from screenshots linked to capacitor from schematics for handiness.
https://imgur.com/a/1kDS7hZ

I have seen serval videos online on capacitor replacement which makes me think I can repair this having the right tools?
Given everything I've mentioned I'm hoping someone can confirm I have traced the source of the problem, that I would be able to repair this, and if so would neighbouring capacitors be damaged and need replaced also given my images.

I believe the correct capacitor is 33uf - 20% - Tant-Poly - Case-B3; I am based in the UK, where would I be able to get a replacement one if this is indeed what I need?

[andrewsawesomr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

I think I found the right capacitor. To check, what is the length and width of the capacitor?
The capacitor is definitely bad, so you need to replace it if you want to try to get a working machine. There might also be sonething else that is wrong, but I would just try to replace the capacitor for now.

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

I've just measured with a tape measure. - 3/32 inch x 1/8 inch (2.38x3.18 mm) approx, sorry i cant be more precise.

Yeah I was thinking there must be something underlying to have caused it in the first place.

[andrewsawesomr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

I found a capacitor with similar dimensions from RS Components.

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Brilliant, ive had a look at your link.

I was able to get approx height of cap, of 1.2mm - and found similar products in spec.
https://uk.rs-online.com/web/p/polym...citors/1213330
https://uk.rs-online.com/web/p/polym...citors/1877181

I notice the varying ESR values, these being 45mΩ and 50mΩ, and compared your link of 70mΩ. Will there be any problems if i replace with a different esr value?

[afarr]

Capacitor ESR value query

I have found a compatible capacitor for a replacement on a A1706 MacBook Pro mid 2013, 13inch.
C7490 location on schematic and the the capacitor spec is 33uf - 16V - 20% - Tant-Poly.
The is varying ESR values, these being 45mΩ and 50mΩ, but no mention of this value on the schematics.

I was wondering is there a specific EST value of mentioned capacitor for a MacBook logic board? And would installing the wrong one effect anything?

Thanks I'm advance.

[reformatt]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Tantalums go short for no reason and burn up. I don't know the actual failure mechanism, I just accept they fail, and replace them. I'm assuming your PPBUS_G3H rail is shorted to ground correct? Biggest issue is probably getting it off the board if it welded itself to the pads, or carbonisation of the PCB. If that is all good, this is a money for jam job.

As far as the cap itself goes, a donor off another MAC should be fine. It's just a decoupling capacitor for the PPBUS rail. It's to prevent local voltage sag during high loads , so ESR isn't overly important (it is a tantalum after all). The ceramics are there to prevent noise etc from the VRM getting back onto the bus to the rest of the machine.

[andrewsawesomr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

OP, as reformatt said, the ESR of the cap doesn't matter, so you can choose the product I linked or any of the parts you linked. Since ESR etc. doesn't really matter, I would recommend the capacitors I linked, since they are much cheaper.
What tools do you have for soldering/desoldering?

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

What tools do you have for soldering/desoldering?

I haven't got the tools yet, but competent enough that I think I can do it.
What tools would you suggest to be able to complete this job?

Also a question on the your product link, would the height of the cap make a difference? As your product is the cheapest, and would be idle.

[andrewsawesomr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

What tools would you suggest to be able to complete this job?

Also a question on the your product link, would the height of the cap make a difference? As your product is the cheapest, and would be idle.

The 0.9mm height differerence shouldn't be a problem. As for the tools, I'm not a surface mount expert, but I think you should be fine with a temperature-controlled soldering iron, solder, flux, soldering braid, and tweezers.

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Excellent, thanks for all your help.

I’ve managed to get everything you suggested bar the solder, all solder seems to be lead-free but seen suggestions to use lead solder. Does it matter which kind I use?

[MicroSMD Lab]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Excellent, thanks for all your help.

I've managed to get everything you suggested bar the solder, all solder seems to be lead-free but seen suggestions to use lead solder. Does it matter which kind I use?

Lead solder has a lower melting point so it's easier to work with (less heat). With what I saw on the pictures, it's possible for one of the terminals to be "welded" to the PCB so keep that in mind if it's very difficult to remove. You may end up damaging the pads but you can always make a jumper with a suitable size wire.
Flood the terminals with lead solder and keep alternating with the soldering iron while gently pushing on the capacitor... better yet, if the capacitor is brittle enough to break then you can remove one terminal at a time.

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Brilliant that’s for all this information, I’ve went for 0.8mm 60/40 solder rosin core.

The cap was breaking away with tweezers so should be able to work at each terminal as you have suggested if I run into that problem.

I feel like I’ve gotten everything covered now, thanks again for everyone’s help.

[andrewsawesomr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

You're welcome. Always good to see another piece of electronics get repaired rathe rthan thrown away.

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Update:

So I've successfully i think been able to replace the capacitor and the MacBook now boots up, but when removing the old solder with the solder braid I've taken of a transistor located next to it. https://imgur.com/etZ8nTV, circled in link.

Its linked to the Thermal Sensor B & CPU High Peak Detection and it is critical, but does not looked to be related to the original problem from the schematics documentation, the problem with this missing now is with the fans now running at full speed and the system is throttling because of it and can not navigate at all bar boot the computer to login screen.

The transistor is at Q5871 (BC846BLP DFN1006H4-3), am i able to replace this similarly to the cap, and if so where would I source this?

[andrewsawesomr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

I couldn't find that exact transistor in stock from RS Components or CPC Farnell, but I did find a BC846BMB transistor (unfortunately you will need to buy 100). I believe you should be able to substitute this, but you might want to wait for further confirmation.

[mon2]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Any general purpose NPN transistor in this package and pinout should work fine. Apple has used them as a low cost thermal sensor on assorted logic boards and hard drives.

For example, this one (or the above one that was suggested):

https://www.mouser.ca/ProductDetail/...9RY5DyUw%3D%3D

You can also try Digikey -> search for the package 'DFN1006-3' and then 'NPN' to find a match.

They are tiny so order a few spares. Did a repair last week with 0201 parts where I lost 2 of them even with precision tweezers before even reaching the PCB pads. One of the parts literally disappeared on me but found it after a search party. The 0201 part was stuck inside the flux drop bubble on the needle of the tube that was used to dispense the goop onto the PCB.

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Thanks for your help this far.

I ordered the part suggested from RS components, but they are impossibly small. I attempted to replace but failed to keep in place, probably the best option would be a reflow oven, and someone more experienced.

But happy I tried it out at least, I mean getting it to power on was a success in itself for my first time.

[mon2]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

Indeed small. To be honest, took a 4k camera on a microscope and a few tries to get it right on my side. My eyes cannot cut it on their own. Usually pretty good on pcb inspection but these are small.

Fir our SMT line upgrade, reviewing a machine that can support 1/4th this component size. The line can support the world's smallest parts. It is on my bucket list and hope to see it live in Shenzhen later this year.

Suggest that you consider,

1) fine tipped tweezers
2) hot air tool - personally use the Best 863 hot air tool from AliExpress
3) amtech or clone flux (AliExpress)

Use the flux with low air pressure but high heat and the part will melt like butter onto the pcb pads. Low low air pressure else the part will go flying.

Curse at Apple while doing the repair but it is a rewarding experience when it is all working.

PS: thanks for the great music from your region - The Pogues, U2, Cranberries (although Dolores moved to Canada later in her life).

[afarr]

Re: Apple MacBook Pro Mid-2017 A1706 - C7490 Capacitor Help

I tried a cheap usb microscope actually good enough quality, but felt my eyes did a better with being able to coordinate my hands properly.

Is there such thing as conducive adhesive?

I’ve had a quick look at the BST 863, but wouldn’t be in the budget right now. But going to ask around to see if anyone knows someone that has something similar, we are lacking in repair shops of this kind here.