Released on September 19, 2014, this 4.7" screen iPhone is the smaller version of the iPhone 6 Plus.

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How to I test the Tristar?

So this 6 is my classmates, she said the screen was broken. Tried a new one, still not turning on. Tried a new battery, charge port and screen. Still dead. How could I test the Tristar without removing it?

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Was the phone working when you received it and before you made repairs?

When you say it is not turning on, I assume you have already tried connecting to iTunes... (did you try just the basic logic board and dock flex?)

There's not a lot to "test" on the Tristar, it is mainly a communication chip so most of the lines are for serial communications. You need an oscilloscope or logic analyzer to really see what's going on. Now, if the phone is dead and it worked before your repair attempt, then I would start at the beginning and check the area surrounding the connectors, especially the battery. Then check if you have shorts on the main voltage rails (PP_BATT_VCC & PP_VCC_MAIN). Then check PP3V0_TRISTAR & PP1V8_SDRAM to see if they are powering the Tristar IC.

Check those out and get back with updates.

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I tried a new screen, battery, and charge port already. It did not look like it had been worked on before. But, the display cables were cut with scissors. I have not tested any voltages yet, I will try that tomorrow. If a voltage rail is missing I will just buy it from them so I can test it and try experiments on it.

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Also when I first got it it was not turning on.

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@refectio So I followed the steps you mentioned. PP3V0_TRISTAR & PP1V8_SDRAM are having 0 volts and no short to ground. Does this mean the tristar chip is is bad?

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@refectio I already checked the main rails off course. They don't have a short but the voltage was too low (0,5 volts on VCC_MAIN)

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So, update on this phone, i still have it and it is working. turns on, works, everything. the thing making it not turn on was the capacitor next to the wifi chip got a drop of water on it and made it short. It still has FMI on because she couldnt remeber her password.

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We recently made a post about using a multi-meter to get a 100% accurate test of the tristar status of good or bad see here: https://www.microsolderingrepairs.com/bl...

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