주요 콘텐츠로 건너뛰기

6s와 유사한 하드웨어 사양의 4-inch iPhone은 2016년 3월에 출시되었습니다. 16/64GB 저장 옵션 및 은색, 스페이스 그레이, 금색 또는 로즈 골드로 제공됩니다. 모델 A1662 및 A1723.

1046 질문 전체 보기

u4020 critical to boot?

Good afternoon,

I'm just researching a water damaged iPhone SE that initially had a VCC_Main shorted that was alleviated by removing one cap.

When connecting to power now, it draws 0.43mA / 0.44mA and U4020 LED Driver gets really hot (freeze spray used to detect).

It controls the "LED Driver" and schematics says it is critical. Is it critical for boot? or if we remove this should we be able to artificially use a light and go into the screen layers?

답변되었습니다! 답변 보기 저도 같은 문제를 겪고 있습니다

좋은 질문 입니까?

점수 0
댓글 달기

답변 1개

선택된 답변

Just to confirm, U4020 is not Stockholm but the Backlight Driver IC. A damaged or defective backlight driver doesn’t stop the phone from booting, unless it is pulling down PP_VCC_MAIN. So check VCC_MAIN to see if it is short or or not giving the proper voltage.

Obviously, a missing backlight driver doesn’t affect the boot either.

You should also probe the backlight circuit as if U4020 is hot, then one of the caps may be shorted on the output side.

해당 답변은 도움이 되었습니까?

점수 3

댓글 6개:

Thank you Minho, Not sure how I got this confused thinking it is Stockholm, must have had different schematics up or something. Will check the VCC_Main voltage and see

VCC_Main is low! 2.9V, I will remove this and see if it helps things.

VCC_Main short up to 3.6V now but still power being drawn is 0.45mA, no obvious signs of heat but removing this chip helped because there was a lot of corrosion, even under it!

Any ideas of probing further with this at all? I really appreciate your help!

What do you mean by "VCC_Main short up to 3.6V " ?

Using a multimeter in DC voltage mode VCC_Main is reading at 3.68V, before removing the LED Driver this was a lot lower

댓글 1개 더보기

댓글 달기

귀하의 답변을 추가하세요

Elliot 님은 대단히 고마워 할 것입니다.
조회 통계:

24 시간 전: 0

7일 전: 0

30일 전: 0

전체 시간: 154