PP_VDD_Main Short to Ground 0 ohms resistance

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iPhone 7 Plus

2016年9月16日に発売。モデル番号は1778,1784。 GSM かCDMAの32、128、256GBがあり、色はローズゴールド、ゴールド、シルバー、ブラック、ジェットブラックがあり。

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Zero Alpha @zeroalpha

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投稿日: 2020年2月24日

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PP_VDD_Main Short to Ground 0 ohms resistance

I have a 0 ohm resistance short to ground on VDD_main. Because there is no resistance I can’t find the cause of the short with my heat camera. There are only 2 things that come to mind.

# A physical short has been caused by some kind of debris or misplacement which I just can’t find even with cleaning and searching thoroughly, or

A surface mount component has failed causing a 0 ohm short to ground. Is this likely and what type of component could cause this?

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I’ve injected current to different points. With 0 resistance there is just no energy loss to detect heat :(

Zero Alpha さんによる2020年2月24日

Have you removed the shields? What model board is it Intel or Qcom? Have you tried freeze spray instead of your thermal cam? Was the board water damaged and maybe put into a microwave?

Chris Stables さんによる2020年2月24日

@imicrosoldering Intel board with all shields removed. Phone failed on Q2101. I removed it but can't solve VDD_main short now

Zero Alpha さんによる2020年2月25日

If Q2101 failed you should defiantly remove Tigris. It has probably been damaged and most likely the cause of the short.

Chris Stables さんによる2020年2月25日

@imicrosoldering Yep, One step ahead of you. I've removed Tigris also. Still 0 ohm resistance short to ground

Zero Alpha さんによる2020年2月25日

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I’ve injected current to different points. With 0 resistance there is just no energy loss to detect heat :( — Zero Alpha
Have you removed the shields? What model board is it Intel or Qcom? Have you tried freeze spray instead of your thermal cam? Was the board water damaged and maybe put into a microwave? — Chris Stables
@imicrosoldering Intel board with all shields removed. Phone failed on Q2101. I removed it but can't solve VDD_main short now — Zero Alpha
If Q2101 failed you should defiantly remove Tigris. It has probably been damaged and most likely the cause of the short. — Chris Stables
@imicrosoldering Yep, One step ahead of you. I've removed Tigris also. Still 0 ohm resistance short to ground — Zero Alpha

Minho @refectio 評価: 221.4千 15 289 807 · Answer 1 · 2020-02-24T18:05:51-07:00

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Minho @refectio

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Usually, the culprit for most shorts is a capacitor as they are placed between VDD and ground. However, there are hundred of capacitors on the PP_VDD_MAIN line so you want to avoid having to remove them all to find the short. Understanding the history of the device and the circumstances leading up to the failure may give you some clues as to where to focus your efforts.

You can also try to apply a lower voltage, say 2V directly to the PP_VDD_MAIN line, bypassing the Tristar/Tigris circuitry, as well as most IC’s. That may allow the thermal camera to pick up a heat signature from the offending component. You can also leave the device in this condition for a short while to see if anything “lights up” because with enough time, even a small trickle current will heat up the offending component a bit.

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What about my 7 plus it was on the charger and then died while on there. Before it got on the charger it had 20% Battery and then maybe 14 minutes later “📵😵📱💥PP_VDD_MAIN SHORTED” so 4 years later I’m trying to recover data to my phone and I already removed one of the capacitors that was most likely shorted. It still isn’t fixed for the short, but it is reading at least 0.01 sometimes. I partially got rid of the short, so I just need to know where it might be shorted. (VDD MAIN should be fine if I removed 1 or 3 capacitors because there is already other capacitors that are on the line, that’s why they put so many so if one or 2 go out, you can just take them off and the short goes away)

D B C さんによる2024年3月13日

@D+B+C measuring 0.00 or 0.01 doesn't really mean much because you are well within the margin of error for most hobbyist multimeters. So maybe you found a capacitor that is shorted and you have improved the situation, manner of speaking, but probably not. But don't let that deter you, keep probing!

Because we are all here to learn, take the rest of my comment in that spirit :-).

Electrical engineers dont put lots of caps on a board just in case a DIY tech removes a few of them. They have some amazing properties, which means you can use them for different purposes. In the context of an iDevice, they are mainly used for noise filtering and decoupling (bypassing).

When you see multiple capacitors in parallel with the same value, or at least in the same ballpark; that is done to get a much larger capacitance without having to use a big-ass cap when vertical real estate is at a premium, like on an iPhone.

Check the EEVBlog for more details: https://www.youtube.com/watch?v=BcJ6UdDx...

Minho さんによる2024年3月15日

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iPhone 7 Plus

PP_VDD_Main Short to Ground 0 ohms resistance

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