Chosen Solution
Hi all, working on an iPhone 6 which wouldn’t charge or connect to iTunes but boots fine from a known-good battery (or did). Having done some metering I decided to replace Tristar and that appeared to go well with 36 nice shiny pads tinned and wicked, and the new A3 chip (Chinese) seemed to go on fine. However when I tried it again it won’t boot from the battery it just boot-loops on the Apple logo, so I had a much closer look around the board in the general area and found that I’d accidentally pulled off a cap when removing the (copious) Kaptan tape I’d used. The chip is C3801_RF on the V_REG 2V line. The interesting thing is that the schematic shows an entry beside this cap which says ‘MAKE BASE=TRUE’ and I’m wondering if this cap provides confirmation that the baseband chip is installed, without which the phone continually boot-loops trying to find the baseband? Anybody come across this before and am I completely on the wrong track? Any other suggestions? I’m going to replace the cap when I get home!
I would certainly replace the cap, especially one of that size. As for the cap providing information…no. All a cap does is store energy. That said, the cap provides this energy to the IC’s when instant energy demands show up and the inherit inductance of the PCB impeded quick delivery of said energy from PMU_RF. During bootup, this ability to deliver some juice quickly may make the difference between BB booting properly or not. Replace it and get back to us, I’d love to hear the outcome. I would also check for any other components that may have been accidentally removed.
