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Comment by bb88 | Hacker News Reader

First thought is that probably a SMD component has shorted itself out. Unfortunately that's default behavior for many SMD components -- short circuit instead of an open circuit.

If the power adapter supplies 20V (which sounds like it might), then any components which might have shorted them selves out could be passing 20V to the other usb power line right next to it.

The other side of the machine probably has another USB controller, which likely explains why it's fine.

So, in short, I don't think this is a problem with USB-C, just a bad luck of the draw that you got a failed component along the way.

Edited to add:

Louis Rossmann's macbook repair Youtube channel is pretty good at discussing why things fail for a mac. https://www.youtube.com/channel/UCl2mFZoRqjw_ELax4Yisf6w

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Actually, it's not SMD components in particular. The failure mode for many MOSFETs and other semiconductor devices tends to be a short. They only tend to fail open if there was enough energy at hand to blow the short clear.

Ah yes, I remember from lab, you'd get a fail open right after you managed to manufacture a temporarily light emitting diode from things that are not normally light emitting diodes (or maybe not even diodes).

We call those "Light Emitting Resistors".

They result when you attempt to violate Ohm's Law.

You can generally diagnose those olfactorily as well as visually. :)

> You can generally diagnose those olfactorily as well as visually. :)

Indeed, my electronics engineering mentor described it as "letting the magic smoke escape". Once the smoke is gone, so is the magic.

Now if only you could capture the smoke and get it back inside the chip.

It would work again!

> exercise Ohm's Law.

FTFY ;-)

Or alternatively, SEDs (smoke emitting diodes).

Old bad electrolytic capacitors often smell like bad fish. Not sure why.

There was this guy called Edison who once made quite a healthy business out of selling LERs. They seem to have lost some of their sheen nowadays but I suspect they'll make a come-back one day in miniaturised form, something like 'nano-LERs'.

Everything's a fuse, it's just a question of how much current it takes to blow.

Indeed! Reminds me of this joke image https://i.imgur.com/TtFotWu.jpg

Unfortunately, in really old houses, I have seen pennies used. Shudder

I had a friend that would fix bad PCBs that had a short in a middle layer by hooking up a car battery and burning up the short. It actually worked.

These days I bet a thermal camera would be great for finding those.

Rossman (see link above) shows how to use 91% isopropyl alcohol to find these more effectively. It evaporates more rapidly at the heat source, so there's your short. I don't know how well this would work to find shorts in middle layers of circuit boards; I am still learning to identify the broken active components on the surface.

It worked without unwanted side-effects? Wow.

> The other side of the machine probably has another USB controller, which likely explains why it's fine.

Unfortunately (well, except in this case) that's true. On the 13inch MacBooks, the ports on the right side have less bandwidth and can struggle with multiple 4k displays

You need to remember what you are asking for here. Two 4k displays already require 30 Gbit/s of bandwidth.

Then they should be labeled appropriately, and preferably use different form factors. There's no excuse from having identical-looking ports that do different things.

That appears to be kind of the point of USB-C-- identical-looking ports which may or may not actually do the same thing. A given USB-C port might be a host port; might be a device port; might be capable of serving in both roles; might support video (over HDMI or DP or some combination of the two) or might not; might support Thunderbolt or might not; might support high-voltage/high-current power delivery or might not... and all on the same connector, so good luck trying to figure out what supports what without looking at manuals.

Same problem applies to USB-C cables. Understandable why (want to spend $100 for every cable you buy?) but intensely frustrating.

I see it as one of the big failings of USB standards in recent years.

USB used to be simple, and they worked so hard to make it so that whatever plug could be plugged into whatever compatible socket.

Then we had USB on-the-go, and issues with then a micro-A port isn't just a micro-A port.

And now we have USB-C and Thunderbolt. Ugh.

We’re well past that point. USB is explicitly designed to have ports with different capabilities, right from day one. Even with USB 1.1 you couldn’t treat all ports equally, since there’s no difference between a port that can give 100mA and one that can give 500mA.

The nice thing about universal things is that there's so many different kinds.

But that would spoil the symmetry!

No, seriously, that sort of thinking is baked into Apple's DNA. Jobs once tried to intervene in memory bus layout on aesthetic grounds.

https://www.folklore.org/StoryView.py?project=Macintosh&stor...

"But look at the memory chips. That's ugly. The lines are too close together."

Surprised more haven't noticed how symmetry had become one of the guiding principles behind all Apple industrial design of recent years.

This ideology has damaged things that used to work fine like the keyboard arrow keys just for the hope of symmetry as visual harmony.

Don't worry! You'll be able to tell them apart by the slightly different logo embossed in black plastic on black plastic lettering on the back of the device.

And there's a black button with black lettering which lights up black if you press it which tells you not to press it again.

https://www.youtube.com/watch?v=AUaJ8pDlxi8

This video is a good one.

Videos like that and personal experience with MBP's since 2009 have seen my wallet go elsewhere.

What is SMD?

He probably means SMT - surface mount technology.

SMT is the technology; individual devices are SMDs, or "surface-mounts" or "surface-mounted".

Beyond terminology, SMD are much harder for an individual hobbyist to desolder, replace and resolder than through-mount, but they are easier for pick-and-place machines to deal with.

If you're prototyping a simple device, you can start with a breadboard -- no soldering. Then you can get a circuit board printed to your spec and use the same components, for low-volume work. If you need high-precision placement, you will probably need to transition to surface-mount.

"Beyond terminology, SMD are much harder for an individual hobbyist to desolder, replace and resolder than through-mount, but they are easier for pick-and-place machines to deal with."

And SMD are smaller, allowing smaller circuit boards and smaller devices.

Surface Mounted Device/Technology (https://en.m.wikipedia.org/wiki/Surface-mount_technology)

Surface mount device: https://en.wikipedia.org/wiki/Surface-mount_technology

Surface Mount Device; sort of the opposite of through-hole, they're both soldering and electronics mounting methods.

https://en.wikipedia.org/wiki/Surface-mount_technology

Surface Mount Device. The name given to components which are soldered directly to the surface of the PCB (printed circuit board). SMD devices are very common now and replace older components which had legs (or leads) which had to pass through holes in the circuit board, also known as "leaded components" or through-hole.

Adding to the other comments, this is in contrast to "through hole" components with leads that poke through holes and are soldered to pads on the reverse side of the board.

I thought it is worth pointing out, the newest rumours from Weibo, all latest iPhone and iPad in 2018 will ship with USB-C to Lightning cable. And all Charger will support USB-PD with 18W.

On some MacBooks it’s common for the CPU to get charger voltage (instead of the usual 1V or so) if the CPU power transistors are damaged (often due to liquid).

That's the thunderbolt port, which is designed to pass full current, that's why it's specific to that port.

From googling for a few minutes, I’d make a guess it’s the intel jhl6540 (thunderbolt/usb-c) that may need to be replaced

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