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iPhone 8 plus - no boot
Hi, I have an iPhone 8 Plus (Qualcomm) with no boot. It had significant water damage when I got it and also a VDD_MAIN short. I cleaned it thoroughly and for the most part it came up pretty clean with just a few areas of minor corrosion. I then found and removed a shorted VDD_MAIN cap, which addressed the 3A draw before prompt to boot when connected to DCPS (although there was still a small draw of about 24mA). When I try to boot the board it goes to around 136mA or sometimes a bit more and then just sits there. I noticed that the transistor Q3201 beside the LCD connector was loose and removed it. Two of the pads were largely gone (the single pin side was fine but the I2C and 1V8_S2 were badly corroded. I've managed to tin and rebuild them and I took a transistor off a donor iPhone 7 and put it back on, but its made no difference, the phone still doesn't boot. While it was off I booted the phone and was getting 1v8 on the pin (which looks like its fed from the other transistor) although it actually read about 1.3v volts initially but then fairly quickly incremented until it got to 1.8, which was a bit weird.
I know you've made a couple of videos on this so just wanted to ask if this transistor (or the one beside it Q3200) are even needed for boot, or are they just to control battery percentage and management etc? Are these part of my no-boot issue or can I ignore them for now and look elsewhere? If so, would Hydra replacement be worthwhile do you think? Grateful for any suggestions or advice
The phone will boot without these transistors, but the phone will boot loop, not charge, and display the wrong battery percentage. I haven't had a single instance where hydra was the issue, so I would not replace hydra, unless you think the water damage got to it. This phone is water damaged, so it could just be about anything...just check all of the main power lines for shorts first.