Revamped version of the iPhone 3G with faster processing speeds. Repair of this device is similar to the 3G, and requires simple screwdrivers and prying tools. Model A1303 / 16 or 32 GB capacity / black or white plastic back.

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Multimeter Question- Battery and Charging fuse


I done a multimeter test on my iphone 3gs battery and charging fuse but i dont know if im doing it right. The board is disconnected from the phone (so no power) and when i place the multimeter (9v) on the board it is readin 0.3Ω on the charging fuse and 0.2Ω on the battery fuse. Is this correct or should it be showing something different? I cant seem to get the phone to switch on and i have done a battery change, tried different chargers and leads. I put the motherboard in my working 3GS and nothing happened so it suggests to me that theres a motherboard problem. Can anyone help me please?

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Not an answer. My phone won't charge B/4 or after battery replacement. Did you resolve your problem? If so, how?


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Danny Puggsy, I wouldn't worry to much about the resistance at this point. The "fuses" are not really fuses. the one referred to as battery fuse is actually a 0.050 1% 1/3W MF 805 resistor and the "charging fuses" are FERR-120-OHM-1.5A inductors. So measuring it in resistance could give you erroneous results. Check for continuity will give you a better idea. Hope this helps, good luck.

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Battery "Fuse"

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Charging "Fuse"

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Hi Oldturkey, Thanks for your reply it is most appreciated. so what setting should my multimeter be on in order to measure the continuity? Sorry to sound like an amateur but i havent really used one of these before on a motherboard, i have a fluke 77IV (cant seem to upload a photo). I'm assuming the motherboard is the issue as i have put it in my working 3gs and the phone doesnt power up. Thanks


Nice meter :-) Anyhow, set your multimeter to the correct mode. Look for the icon that looks like a sound wave, on your meter it is at the 2o'clock position.Touch one of the probes off one of the points of the "fuse", touch the other probe off the other point. If you hear a beep or a buzz, there is an electric connection between the two points, which means it has continuity, if there is no connection you will not hear a beep or a buzz and the display will give a reading of 0.


Forgot to ask if you have done a hard reset when you changed the board. Have you tried a different dock connector? It could shorten out the circuit if faulty.


For some of the voltages on your logic board, check my answer on this question How to replace the power IC, iPhone 3GS logic board?


Thank you for the advice :). I will check these when i get home, i havent chnaged the dock connector yet but i have got one there ready to go so i shall try it, thanks. No i didnt do a hard reset when i put the motherboard in my phone as there was no power, which is why im suspecting a motherboard issue, is it worth soaking the board in isopropyl alcohol just incase there is any corrosion?


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