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iPhone 7 no sound - done Audio IC already  

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wrightg_belfast
(@wrightg_belfast)
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20/02/2020 11:23 am  

Hi, hoping you can help with this. I have a 128Gb iPhone 7 with no sound. Apparently it just started making an interference-type noise through the speaker and no sound since. When I tried it, it made the same sound, although when I went to voice memos the button wasn't greyed out; it would let me press it and the recording tried to start then went off immediately. It also doesn't take a particularly long time to boot (maybe a minute) but despite this I removed the audio IC, wicked the pads (lost a few NCs but nothing else) did the C12 jumper only, took a chip off a donor, re-balled and it put it back. Doing exactly the same thing after the audio IC work of course!

I was a bit dubious that it was actually audio IC because it didn't really have any of the other symptoms but thought I'd do it anyway just to be sure. It's still making the interference noise and no sound, so I'm wondering is there any other component which could be causing this rather than audio IC? I'm thinking one/both of the speaker amp ICs maybe? I've tried different housings and changed the speaker unit of course, just to rule out hardware faults but it does the same whatever housing it's in. I'd be grateful for any thoughts or suggestions you may have on this.

Thanks


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Mike
 Mike
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20/02/2020 11:27 am  

Try the north speaker amp which is above the cpu.  Sometimes it cracked.  

 

Honestly, I've done so many audio ics now and if it doesn't have the classic symptoms (ios 12: long boot time & grayed out speaker button; ios 13: grayed out wifi upon bootup and unable to record in voice memos), then it's not the audio ic...it's something else.


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wrightg_belfast
(@wrightg_belfast)
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20/02/2020 6:37 pm  

Hi, thanks for this. Thinking about what you'd said I remembered that when I first got this I'd changed Tristar as it wasn't booting. Went back and had a closer look; found that I'd clipped the edge off the close-by speaker amp IC (probably when removed part of the shield around the Tristar IC to make it easier to get at it). It was only a tiny nick but it looked as though the corner ball maybe wasn't making contact so I took it off, took one from a donor, re-balled it and put it back on, and BINGO! Sound working great now. I haven't yet checked baseband to make sure I'm still getting a signal(!) because another problem has now popped up; the power button doesn't work in any housing although the phone boots fine when prompted by tweezers at the connector. I'm also getting a small 24mA draw on DCPS before prompt to boot (not sure if this is linked). Have you ever come across this power button thing before? The connector looks fine and there's no water damage on the board and I'm getting a diode mode reading of about 1.10 on pin 13 which is the same as another board I have here presently. As ever, grateful for any thoughts or suggestions 

Thanks


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Mike
 Mike
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20/02/2020 7:03 pm  

connect the dcps to the logic board by itself and see if the 24mA goes away or not.


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wrightg_belfast
(@wrightg_belfast)
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20/02/2020 7:36 pm  

Hi, no difference with board out, it's still drawing 22mA on DCPS before prompt to boot. Boots fine with the tweezers shorting pin 13 to ground. I'm getting 1.5v on pin 13 once it boots, and the large cap C4401 isn't shorted. This pin is connected to a few Zener diodes and a resistor; I suppose I should just try to check each component in diode mode and compare with a known-good? Or is there anything else you can think of?

Thanks


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Mike
 Mike
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23/02/2020 8:17 am  

I can't think of anything else.  In my experience, these problems are often hard to find the underlying problem.


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