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3rd Generation high performance tablet computer released by Apple in October 2018. Models A1876, A2014, and A1895.

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USB C Port Replaced, Only charges with one cable orientation

I just successfully replaced a worn-out USB C port in my iPad Pro 12.9" - 3rd Gen. However, when I try any combination of Apple/3PP cables and adapters, the device will only charge with one orientation of the cable. My iPhone 15 Pro charges on all of the same setups in both orientations.

It was my understanding that USBC port were all bi-directional and should charge regardless of cable orientation. Is this an errant install on my part? Would there be such a thing as a USBC port that only charges in one direction?

Is it possible that there is a component on the actual logic board or connection between the port and logic board that would preclude charging with an 'upside down' placement?

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Interestingly enough, although the USB-C port is bi-directional, it does not use the same signals in both orientations. There are actually separate data communication lines for one orientation vs. the other. Here are a couple of pictures from the All About Circuits website.

Guide to USB-C Pinout and Features - Technical Articles

Here's the receptacle mounted on the motherboard.

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And the plug on the end of the cable.

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As you can see from the first picture, there are actually two TX channels and two RX channels. If the pins on the motherboard connector aren't connected or are shorted, then it's entirely possible for one set of comms to work while the other doesn't; i.e., it will work in one orientation but not the other.

It's also possible the D+ and D- pins could be unconnected on one orientation; this would keep it from being able to communicate over USB 2.0 protocols. There's only ones set of D+ and D- signals; on the receptacle they're wired together to make the port bidirectional, while on the plug there's only one set.

So yes, it means that some of the signals on your connector aren't working; at this point it's impossible to say whether it's a connector problem or some other issue with the USB port, but given you've just replaced the port I'd put my money on a port or pin issue.

The article I referenced has an excellent explanation of how the bidirectional stuff works; that may help you diagnose the issue with your port.

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After reviewing that article, it looks like it's definitely supposed to be flippable. I'm going to accept for now at least that it's mostly likely whatever caused the original port to fail also affected the internal component that the port connects to. Thank you for your help! I'll have to deal with a one-sided charging experience until i feel like digging in more.

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Hi @aeringray

Don't know how Apple wired it but looking at the standard USB-C pinout for it to be bi-directional as far as supplying voltage to the input, the A4 & B9 and A9 & B4 pins would need to be connected together in the device.

The Ground (or Earth) pins wouldn't have to be connected together but would still have to be connected to earth in the device.

Looking at a close up image of the USB-C port, taken from Step.35 of the ifixit iPad Pro 12.9" 3rd Gen USB-C Charging Port Replacement guide, presumably the connector only has 20 pins (10 on top row, 10 on the bottom row?) and not 24 pins and the earth is connected via the connector's metal enclosure.

Hopefully this may help to sort out what the problem is.

Block Image

(click on image)

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This was a fascinating read! It never occurred to me that Apple would have a non-standard USB C port, since I thought the entire point of changing from their lightning port was to standardise and upgrade power delivery and sync speeds. The old port I removed and the new one I put on (the one in the guide you linked) do indeed only have 20 pins (10/10). I am curious how I was able to achieve bi-directionality before. My wife happens to have an identical iPad with a fully-working port, and was able to charge in both directions with everything I tried earlier. Logically, this kind of tells me that while it's interesting and slightly confusing that the number of pins might differ from a standard connection, that it still might be more likely that the problem could be with what the port connects to on the iPad logic board rather than the port or cable. Does that seem like a reasonable assessment? I am somewhat experienced in basic repairs, but troubleshooting the actual schematics has thus far escaped me. Thanks!

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@aeringray

You can get various types of USB-C connectors i.e. 6, 8, 10, 12, 14, 16, & 20 pin as well as the standard 24 pin but they should be all the same as to what function each individual pin has.

It would be unusual however to rely solely on the port's metal enclosure as an earth connection rather than having the requisite pins and the metal case.

It's just that some devices either don't have all of the required features available from a fully wired USB-C connector e.g. fast charge, power delivery etc perhaps only some or none at all except standard USB2.0 i.e. 5V power and data.

It could be on the logic board or even catered for in the USB-C charge port board although as long as you connected all of the pins i.e. top and bottom rows then it should work either way

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