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iPhone 7 boots, charges but no data access

Hi,

I have a weird situation, an iPhone 7 came to me, it boots fine and charges. I replaced Tigris (because with freeze spray this got very hot quicker than any other component) and it asks you to Trust the device, then the connection times-out according to 3UTools.

I did reflow Tigris again just in case some solder balls weren’t 100% good - same situation.

PP1V8_SDRAM is giving a Diode resistance reading of 158 when schematics say it should be more around 280 …

I have freeze sprayed the board and PP_VAR_SOC gets hot first and so does PP_USB_5V0 in the top right corner of Tigris.

I might order another Tigris and try again, but any thoughts on this?

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Why did you do a freeze spray test on a device that boots fine? That’s for finding shorts and in order to determine that you have a short, you have to probe the board first. Besides, of course Tigris is going to heat up first…that’s where all the current flows when the phone is connected to a charger.

So what is the original problem you were trying to fix? Was it the connection timeout? If so, then it is probably a Lightning Port or Tristar issue. If it is something else, then please elaborate.

I don’t mean to be harsh but you have to troubleshoot a phone properly before applying any heat, especially when you are starting out, otherwise you risk causing more damage than you can repair. Identify the issue, then try to figure out what part of the phone handles these functions. Then try any relevant small parts before even thinking of replacing IC’s. Only when you have ruled out component issues can you start to look at micro-soldering options. Then probe all relevant subsystems. I’ve seen PP1V8_SDRAM lines at <200 before so look elsewhere…don’t forget, the phone boots fine and it would not do that if PP1V8 was bad.

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Thank you for the reply, I'll note that for future reference, I suspected Tigris because it deals with USB communication, The device draws normal current so I was suspecting it was less Tristar and more Tigris. It was non conductive freeze spray, I also didn't inject voltage with probes, just observed where got hot on a normal boot sequence.

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Tigris is the charging IC, Tristar is responsible for communications.

The point I was trying to make is that you have to develop a thorough troubleshooting process (for dead phones/complex issues) otherwise you will come to erroneous conclusions which will make you do repairs for nothing. This isn't just directed at you, there will be hundreds of people who will see this Q&A over the years.

There's nothing wrong with freeze spray, it's a tool like any other. You just have to develop enough knowledge to know when each tool can help you rather than give you false leads.

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Elliot 이(가) 영원히 고마워 할 것입니다.
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