Launched in spring of 2014, the OnePlus One packs a 5.5" display and runs the Android-based CyanogenMod 12S operating system.

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SIM card detected, but no service

I have gotten my hands on an old, out-of-warranty OnePlus One which can read/detect a SIM card, but it can't get service on it. I tried changing it from an older SIM to a newer, higher capacity one, but that didn't do anything, so the problem is with the device itself. I tried to get it fixed from some local repair shops, but they said that there's a problem with some particular SIM-related component and that's difficult to come by.

I'm interested in trying to fix this myself and learning about these things in the process. How can I troubleshoot this? How do I identify which part exactly is the problem? Where do I start?

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A good place to start debugging a circuit is by looking at the SIM reader's pinout. SIM card readers have some voltages on their pins that should always be present in order to correctly detect and access a SIM card. The pinout (and some other useful info) can be found here: http://www.technoburst.net/2014/03/sim-c.... You should measure the pins and see if their voltages are correct.

If all the voltages are present, you could start looking for the GSM modem on the board, see if that's getting power on its Vcc - pin, check if the trace to the antenna isn't interrupted, see if there's any kind of damaged filter in the way (some antenna's are used for multiple things, for example, the iPhone 4S uses one antenna for Wi-Fi and GPS signal and separates the two frequency bands with a filter. If that filter is broken, the signals are mixed and won't be received propperly by their respective chips).

Unfortunately, I don't know exactly where all the chips on the board are (and can't seem to find a schematic for this device). Sadly it seems that most of the chips are underneath some ESD - shields, so you'll need a heath gun to pull these off. But, if you have a heath gun and a multimeter laying around, I'd strongly encourage you to try and debug the board :)

Best of luck!

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Now that sounds like a handful of good ideas! I'll see how far I can get. I've always worried that I might break things more in an effort to try and fix them, but I guess I'll go on in the name of science. Thanks for the advice!

http://imgs.xkcd.com/comics/appliance_re...

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Do you mean SIM or Mico-SD, i ask because of your reference to storage (higher capacity). If SIM, then you may want to try to OEM unlock (jailbreak) the phone because it may be carrier locked to a specific SIM service.

If Micro-SD, try using a PC to format the card in NTFS first, then re-install in the phone while the power is off and then power on.

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No. I was referring to the SIM card storage capacity (48k, 128k, etc.), but that's not relevant. The phone is unlocked. The OnePlus One isn't sold network-locked anywhere, AFAIK.

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Aalaap Ghag will be eternally grateful.
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