iPhone XS U3300 Short

Question

iPhone XS

2018年9月21日に発売されました。モデル番号A2097, A2098、GSM もしくはCDMA / eSIM もしくはナノSIM / 64, 256、512 GB / シルバー、ゴールド、スペースグレイ。(正しい発音は"iPhone 10 S.")

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Colby Morris @colbymorris5220

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投稿日: 2022年1月29日

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iPhone XS U3300 Short

Hello. I have a strange problem with an iPhone XS motherboard which I recently began working on.

When the power supply is plugged into the motherboard, it immediately draws a ton of amps and gets EXTREMELY hot. I separated the motherboard, and narrowed it down to the U3300 chip. I put some rosin smoke on it, and noticed that there is only one pad of the chip which gets hot. I replaced the chip, and still, the short was there. The pad which gets hot is on the PP_BATT_VCC line, which tests fine with a multimeter. Does anyone know how to fix this issue? All the other capacitors look fine on the line. I have come across this same issue multiple times on some iPhone XR motherboards but I couldn’t figure out how to fix it. Thank you for your help

Update: I think the board is shorted to ground by the one pad that overheats but i’m not sure how to fix it.

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bert.harmidomski @tojaert 評価: 5千 11 6 1 · Answer 1 · 2022-01-29T13:48:14-07:00

bert.harmidomski @tojaert

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hello Colby,

it is extremely important how many amperes it is and at what point you notice the short circuit. Start by making friends with your multimeter. It is really a friend of every microelectronics. If the short circuit appears immediately after turning on the voltage, you probably have a shorted PP_Bat line. You have to confirm it. If not, you'll probably find it in a different baseline right after you try to run it (when you turn on the voltage).

On the other hand, use a multimeter to check the pads under the Tigris IC that you suspect are short-circuited. Enter the measurement result here, I will try to help you interpret it. If it is actually PP_Bat the result will be close to 0.000 and you will look for the short elsewhere. It is also likely that you have a problem with a properly seated chip. It really takes training - it won't come by itself :-) (get a time for it). If I'm right, the measurement in the PP_Bat line will be around 0.400

-regards and fingers crossing

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Hello, thank you for your answer. The short does appear right after the voltage is turned on, so it must be a PP_BATT_VCC short.

The pads under the tigris IC are shorted, they come up with readings of 0.000. However, the line's readings from the battery connector do show as 0.400. I find that strange since the line doesn't work properly but it's readings show as normal. The certain pad that gets hot gets extremely hot, and there are no other shorts from what I can see. I look forward to your response and once again thank you for your answer

Colby Morris さんによる2022年1月29日

to understand eachother well - when you do a Tigris IC measurement from the battery port field, have you 0.400? When the measurementing on the other side in fields a1-a7 (pp_bat_vcc) in position u3300 (Tigris ic is off) have you a short circuit? If yes, take off temporality r3380 (pmu_bat_sense) and check pins 235-236 on interposer. We’ll solve this problem.

bert.harmidomski さんによる2022年1月31日

Do you think it could be a capacitor causing the problem? The pads under the Tigris IC come up as 0.000 when the IC is removed. The entire line is 0.000 when the IC is removed. I could try taking off r3380 however i'm not sure what chip that is, do you know what part of the board it is on? Thank you

Colby Morris さんによる2022年2月1日

Colby, r3380 is a V sensor in the form of a charger resistor, controlled by the main PowerManagementUnit (PMU). The pins on the interposer provide V to the motherboard. To understand this you have to see the XS schematic. Find one and try to read it, it's very simple. But if you have a short circuit under the charger, you need to find it. A short line (not long) goes through the other side near the battery socket. There are only a few capacitors there. Check everything there and change if you find shorted. That's it, no birds. If you have a problem, write an e-mail via my blog (details can be found in the profile description) - I will prepare a manual for you with photos and indications of measurements.

bert.harmidomski さんによる2022年2月2日

I replaced r3380 and a few other capacitors on the line, and now it has a normal reading! But, u3300 is still getting extremely hot. I noticed that when I test VDD_MAIN to ground, my multimeter just beeps instead of giving me 0.300. Maybe PP_VDD_MAIN is shorted?

Colby Morris さんによる2022年2月2日

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