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Mechanical USB problem?

Tue Mar 25, 2014 10:15 pm

Not sure if there is a mechanical issue with the RaspberryPi USB connectors, whether I've just been unlucky, or maybe I'm getting clumsy in my old age.

Since the introduction of USB ports, I've been presented with computers to repair from time to time with mangled USB connectors. The most common problem is bent or broken contacts. I've generally assumed this to be the fault of the user, probably due to rough treatment or attempted insertion the wrong way up.

However, when I got my first RaspberryPi model A a few months back, I noticed the USB was very tight when plugging in peripherals. Within a day or so I'd managed to bend one of the contacts. I changed the board USB connector for one purchased from Spiratronics and its been fine ever since.

I'd just about forgotten this experience until yesterday, when a second Model A arrived. I plugged in an Edimax wifi dongle and the Pi failed to boot. Same problem. The two outside connectors were doubled back.

Now before you write me off as a knuckle dragging Neanderthal, just let me say I also have 3 Model B Pi, some of which have had the same devices connected to their twin USB ports, with absolutely no problems. I regularly handle many other model B boards which are used by our Computer Science students. Also, when I plug my Pi peripherals into my laptop, they go in easy but are firm when fully inserted.

So my conclusion is that the single USB connector fitted to the model A is at fault. But I'd love to hear from anyone else with similar problems.

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Re: Mechanical USB problem?

Tue Mar 25, 2014 10:57 pm

I also find the USB port on my model A very snug, but, despite my ham-fisted handling of the device, there's no sign of any damage to the port. I swap devices quite a lot as I only sometimes have a hub attached to it and choose between a wifi dongle for headless operation or hub + keyboard + wifi on other occasions.

My experience is based on a sample of one; as you have a sample of two it's difficult to know if you're unlucky or I'm lucky.
Last edited by RobHenry on Wed Mar 26, 2014 12:36 am, edited 1 time in total.

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Re: Mechanical USB problem?

Tue Mar 25, 2014 11:06 pm

To be honest I think the USB connector is quite robust but like all things electronics if you're brutal or abusive then don't expect them to last. :)

Richard S.

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Re: Mechanical USB problem?

Wed Mar 26, 2014 1:45 am

Me too. I've got two model Bs running perfectly, but I thought the Edimax dongle was a bit tight, fitting into my model A USB port. Shortly after this, the model A wouldn't boot. I moved everything to a working model A, and it failed in the same way. Eventually I cottoned on, and realised that the resistance I'd felt when inserting the dongle was due to it first hitting the ends of the USB connector pins, and when I continued pushing, folding them up inside the socket on the Pi. This meant that the USB was then shorting out, and crashing the Pi.

Fortunately, somebody at work was a dab hand with a paper clip, and managed to hook it around the connectors, and pull them flat again. Having now inserted USB plugs successfully, it's pushed the connectors down flat inside the plastic tongue of the USB socket, where they're supposed to be, and all is sane again!

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Re: Mechanical USB problem?

Wed Mar 26, 2014 1:45 pm

wimble wrote:Me too....
Thanks for that confirmation.

It's difficult to see how you can "abuse" a USB connector if you are just plugging in (the correct) mating connector.

On closer examination, I think I can see what the problem is. There are 6 spring clips which provide some resistance so that the external device connector does not drop out.
USB_Pi_A.JPG (63.88 KiB) Viewed 1140 times
The 2 clips shown in the photo are just over-tensioned. So when you try to plug a device in, the external device connector is pressed up hard against the pin side of the Pi connector and cannot ride up over the Pi connector pins. Result: it just tries to push the pins out of the way.

So here is my advice: if you have a board where the USB insertion resistance is higher than it is on your PC or laptop, turn the Pi over (as in photo) and carefully bend these 2 clips out a small amount....

...that's assuming you can't be bothered to send the Pi back to Wales!

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