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Bad USB-C cable destroys laptop

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Re: Bad USB-C cable destroys laptop

#131

Post by Trellmor »

simoncion wrote: post #93
Perixoog wrote: post #83

Earlier quoted context omitted.

>I wonder if this one cable was miswired or it's something consistently wrong with the product. He bought more to find out: https://plus.google.com/+BensonLeung/posts/EBGMagC46fN

> He bought more to find out: I don't think so. From TFP: "Here are some pictures of the torn down SurjTech 3M cable that fried my Pixel." Cable, singular. :)

From one of his comments

>I ordered one more of each of Surjtech's products before they pulled their listing today, so yes.

Re: Bad USB-C cable destroys laptop

#132

Post by pluma »

Spooky23 wrote: post #98

I think at some point Amazon should take some heat. They should at least de-emphasize uncertified cables or require vendors to have licensed the USB logo. If you buy a power strip, even a cheap one, you at least get some assurance that it is UL rated and probably won't burn your house down. USB isn't just a keyboard connector anymore... We should have some assurance that cables are legit and safe.

Amazon in Germany happily sells you power strips / connectors you can't use in Germany without effectively voiding your insurance if your house burns down (e.g. T-connectors that let you connect two Schuko plugs to a single wall outlet without a cable).

Granted, for some of them it adds a small disclaimer "Only for export" but let's be honest: if you're selling to consumers, you're not selling for export.

Re: Bad USB-C cable destroys laptop

#133

Post by culturestate »

ackfoo wrote: post #115
paulmd wrote: post #39

Earlier quoted context omitted.

Electrical faults are just a fact of life. Wires fray, cables get tugged, or are miswired from the factory. And you just know that sooner or later some genius is gonna jam a butter knife in there for the hell of it. The basic USB spec requires that all ports be protected with a small self-resetting polyfuse for exactly this reason. I don't know if the Type-C or USB 3.1 specs includes something similar - I would assum…

I found a USB Cellular data adapter in the trash and plugged it in to my MacBook Pro, which instantly shut down. Rebooted, and the USB port did not work. Shut it down and left it for half an hour, and, yay, all working again. Disassembled the adapter. Turned out to be a dummy used for display. No guts, just a steel bar across all four pins of the USB connector. Looked real from the outside. It was a very, very stupid…

Plugging random USB devices into your computer is a bad idea, full stop -- miswired or not. "I found this in the trash and plugged it in" is the bane of CISOs everywhere.

Re: Bad USB-C cable destroys laptop

#134

Post by lsaferite »

drewm1980 wrote: post #122
CydeWeys wrote: post #50

Earlier quoted context omitted.

USB-C does lots of things, including high voltage charging, backwards compatibility, and reversible orientation. Yeah, you could make it simpler, but then you'd have to start giving up some of those features, at which point now you've just reinvented USB-A again. It's just as complicated as it needs to be. And for godssakes, the pin-out diagram isn't that complicated; it only has 24 pins! There's no excuse for flippi…

Oh christ... Those pins are actually different signals? When I bought a nexus phone and looked at the new connector I assumed they were just trying to use tricks to reduce contact resistance or something.

Well, the USB 2.0 pins are mirrored so there is no negotiation needed to orient the plug. The others can be mirrored or not, depending on how it is operating. Negotiation can change the job of several sets of pins.

Re: Bad USB-C cable destroys laptop

#135

Post by lsaferite »

userbinator wrote: post #102
CydeWeys wrote: post #50

Earlier quoted context omitted.

USB-C does lots of things, including high voltage charging, backwards compatibility, and reversible orientation. Yeah, you could make it simpler, but then you'd have to start giving up some of those features, at which point now you've just reinvented USB-A again. It's just as complicated as it needs to be. And for godssakes, the pin-out diagram isn't that complicated; it only has 24 pins! There's no excuse for flippi…

"only" 24 pins? That's still 6 times more than the previous standard...

Have you read the spec on what it actually allows though? The fact that it can do USB 2.0 + USB 3.0/3.1 SS + AltMode + 100W Power (bi-directional) all at the same time is... impressive.

Re: Bad USB-C cable destroys laptop

#136

Post by cesarb »

Zardoz84 wrote: post #130
cesarb wrote: post #44

Earlier quoted context omitted.

That's worse than a short. A short pulls the Vbus to 0V, leading to high currents on the source, so whatever overcurrent protection it has kicks in. What he had here, instead, was -5V on the Vbus pin, way outside the acceptable voltage range (which is probably something like from -0.5V to 5.5V). It's no wonder everything fried. The protection against reversed voltages like that would be a crowbar diode between Vbus a…

A diode crowbar or a single would imply a drop of ~0.6v on the line so you always would get 4.4 volts . However there is other kind of protections like this : http://www.edn.com/design/analog/4368527/Simple-reverse-pola...

From what I understand, a crowbar diode is a reverse-biased diode put in parallel with the bus, not in series. In normal operation (correct polarity) it doesn't conduct, since it's the "wrong way", and there's no voltage drop since it's not in series with the circuit.

But when the polarity is reversed beyond the diode's voltage drop (that is, beyond -0.6V in your example), the diode is now the "right way" and conducts, limiting the reverse polarity voltage to the diode's voltage drop (in your example, it won't get below -0.6V).

However, that means that all the reverse-polarity current goes through the diode, in effect a short (like putting a physical crowbar across the battery terminals). If the diode holds long enough, the voltage source's short-circuit protection (be it a fuse, a polyfuse, or something else) should cut the current and all is (mostly) fine.

Re: Bad USB-C cable destroys laptop

#137

Post by joshvm »

userbinator wrote: post #102
CydeWeys wrote: post #50

Earlier quoted context omitted.

USB-C does lots of things, including high voltage charging, backwards compatibility, and reversible orientation. Yeah, you could make it simpler, but then you'd have to start giving up some of those features, at which point now you've just reinvented USB-A again. It's just as complicated as it needs to be. And for godssakes, the pin-out diagram isn't that complicated; it only has 24 pins! There's no excuse for flippi…

"only" 24 pins? That's still 6 times more than the previous standard...

To be fair it's really 12 times 2 to allow the cable to be reversible. USB2 had 4, USB3 had 9. Apples to apples you should compare 8 and 18, but the previous two standards weren't reversible.

Re: Bad USB-C cable destroys laptop

#138

Post by teraflop »

legulere wrote: post #125
teraflop wrote: post #46

Earlier quoted context omitted.

> Each cable needs one of 3 resistors depending on them being a A/B-to-C cable, 1.5A C-to-C cable, or 3A C-to-C cable. No, for C-to-C connections, the resistance is provided by the host ("downstream-facing") port, not the cable. The resistor in an A-to-C cable is basically emulating the signal that would otherwise be provided by the host. There's no such thing as a "1.5A C-to-C cable"; all type-C cables are required…

> There's no such thing as a "1.5A C-to-C cable"; all type-C cables are required to deliver at least 5A. 1.5 A is required to be supported by USB-C, while 3 A is optional. Everything over it is covered by USB Power Delivery, which requires a marking of the cable which of the 5 profiles are supported.

After re-reading the spec, I think both your comment and mine are slightly wrong. Connectors must be capable of handling 5A; cables are required to support at least 3A. (See sections 3.1.2 and 3.7.7.4.) You're correct that higher power requires USB-PD.

Re: Bad USB-C cable destroys laptop

#139

Post by scld »

qb45 wrote: post #69
scld wrote: post #61

I guess he learned that step 1 should be using the ohmmeter and step 2 should be plugging it into hundreds of dollars of equipment.

Do you really test each USB cable you buy like that?

Definitely not, I would buy cables that had already been reviewed by a very thorough user like him! But this guy has made it a hobby to buy different USB 3 cables and try them out. If I was doing that, I would have made a continuity check test rig to measure point to point and also measure the pullups that he usually ends up measuring by hand.

Re: Bad USB-C cable destroys laptop

#140

Post by Dylan16807 »

drewm1980 wrote: post #122
CydeWeys wrote: post #50

Earlier quoted context omitted.

USB-C does lots of things, including high voltage charging, backwards compatibility, and reversible orientation. Yeah, you could make it simpler, but then you'd have to start giving up some of those features, at which point now you've just reinvented USB-A again. It's just as complicated as it needs to be. And for godssakes, the pin-out diagram isn't that complicated; it only has 24 pins! There's no excuse for flippi…

Oh christ... Those pins are actually different signals? When I bought a nexus phone and looked at the new connector I assumed they were just trying to use tricks to reduce contact resistance or something.

If you're using the plug to do USB, you only use the pins on a single side. It's also possible to use DisplayPort and USB 2.0 with the pins on one side.

You use the pins on both sides to do four-lane DisplayPort, or DisplayPort and USB 3 at the same time, or Thunderbolt.

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