iPhone 7 Vdd main Short.

Question

iPhone 7

Rilasciato il 16 settembre 2016. Modello 1660, 1778. Disponibile come GSM o CDMA / 32, 128 o 256 GB / Rose gold, gold, silver, black e jet black.

2264 Domande Visualizza tutte

AGS @ags_studio

Rep: 243

6

22

Postato: 31 ott 2018

Opzioni

iPhone 7 Vdd main Short.

Hi everyone.. and specially @refectio SIR :)

I have an iphone 7 with vddmain short.

The phone story is very normal, client said, he just put out the phone from his pocket and find it off.

I check it with DCPW, they show.

1,2 Volt and 1.4 Amp.

(my DCPS voltage down automatically when i connect short phone and it i manually up the voltagage button, nothing happen and remain same.

The back lower part is hot.

The hottest ic is q2101 and Tigris u2101.

I put out both of them and check the short present.

i change both ic’s but short remain.

Usually i check with Freez spray and always find the bad capicitor or ic, but in this case i cant find nothing strange.

Anybody has a suggestion plz?

Thanks

Risposto! Visualizza la risposta Anch'io ho questo problema

Questa è una buona domanda?

Sì No

Punteggio 2

Aggiungi un commento

1 Risposta

Soluzione Prescelta

Minho @refectio

Rep: 221,4k

15

289

807

Postato: 31 ott 2018

Opzioni

Hello AGS. It’s normal for Tigris and Q2101 to be hot as that is where all the current flows once VDD_MAIN has been “created”.

The best way to find a short on VDD_MAIN is to “inject” 4.2V directly on VDD_MAIN. There’s a nice test point directly on the board, near the Home Button connector that you can solder a thin wire to. Then look for a heat signature. While the back and lower part of the board is warm, it may be a red herring (a false lead) leading you to believe the problem is there. Check all the areas that have VDD_MAIN present (use ZXW to find these areas). For example, remove the CPU shield and freeze that part of the board to see if anything (perhaps C1910 if you have an Intel board) heats up first. Freeze spray usually requires several attempts, focussing on one part of the board at a time.

Jessa did a great video on Freeze Spray vs Thermal Camera, you should check it out.

Questa risposta è stata utile?

Sì No

Punteggio 2

7 Commenti:

Thanks @refectio . I already put out metal shiled, and will try injecting 4.2 Volt and let you know.

Could u plz explain my why in some videos, the guys put put q2101 and then inject voltage manually??? i dont understand the reason why inject after put out q2101 from the board. Thanks

1 nov 2018 da AGS

By removing the MOSFET, you can't have any of the VCC/VDD voltage going back to the battery via the MOSFET because that circuit is cut. However, unless the MOSFET is defective, it doesn't really change much because the MOSFET has a body diode that impedes current flow back towards the BATT_VCC line.

1 nov 2018 da Minho

@refectio sir := thanks a lot.. Infect the bad capacitor was : c1907.

I read your old post, and u explain, if the DCPS limit the voltage, we can set MAX current and 2 voltage for verify the hottest component.

In this way i solve the problem.

Cuold u plz explain me also the difference between amp and Voltage.

I explain better. For example in this situation when i find out the short my DCPW show : 2.2 Volt and more then 3.5 AMP.

I know the voltgae limit for VCC MAIN is almost 4.2 Volt, but when the AMP become dangerous for motherboard??? how many amps vdd main support???

And thanks again for your help sir..

You are my ideal and hope to become like you in the future :)))

3 nov 2018 da AGS

Individual components will get damaged depending on their specified ratings.

So capacitors will blow if you exceed the voltage rating and resistors will blow if you exceed their power rating (Power is equal to Voltage X Current : P=V x I). Coils (this includes ferrite beads, aka. filters) will blow if you exceed their current rating.

As for IC's, they are a combination of all three depending on which part of the internal circuit is affected.

If you look at a schematic, say the iPhone 6, check out the specs on the PMIC page. PP_CPU is spec'd at 7.65A and PP_GPU is spec'd at 3.45A. If you do the power calculations for all of those voltage rails, (plus the BBPMU), you will come to the (maximum) total power consumption of the device. You would then reverse calculate that against the PP_VCC_MAIN voltage to see how much current it actually draws from a battery or DCPS when performing at maximum capacity. It's surprisingly high.

4 nov 2018 da Minho

For fun, let's do some math (P=Vx I):

PP_CPU: 0v95 x 7.65 = 7.2W

PP_GPU: 0v95 x 3.45A = 3.2W

PP_VAR_SOC: 0v95 x 1.8A = 1.7W

PP1V8_SDRAM: 1v8 x .54A = .98W

PP1V2_SDRAM: 1v2 x 1.6A = 1.9W

PP0V95_FIXED_SOC: 0v95 x 3.3A = 3.1W

Just those main rails can draw and dissipate 18W. When you add in all the other PMIC (~5W) and BBPMU (~5W) outputs, it's easy to estimate almost 30W at maximum specs.

Now go back and calculate this from the input voltage of 4.2V and you get

P = V x I or I=P/V

I = ~30W / 4.2V

I = ~7A

4 nov 2018 da Minho

Mostra altri 2 commenti

Aggiungi un commento

Thanks @refectio . I already put out metal shiled, and will try injecting 4.2 Volt and let you know.

Could u plz explain my why in some videos, the guys put put q2101 and then inject voltage manually??? i dont understand the reason why inject after put out q2101 from the board. Thanks — AGS
By removing the MOSFET, you can't have any of the VCC/VDD voltage going back to the battery via the MOSFET because that circuit is cut. However, unless the MOSFET is defective, it doesn't really change much because the MOSFET has a body diode that impedes current flow back towards the BATT_VCC line. — Minho
@refectio sir := thanks a lot.. Infect the bad capacitor was : c1907.

I read your old post, and u explain, if the DCPS limit the voltage, we can set MAX current and 2 voltage for verify the hottest component.

In this way i solve the problem.

Cuold u plz explain me also the difference between amp and Voltage.

I explain better. For example in this situation when i find out the short my DCPW show : 2.2 Volt and more then 3.5 AMP.

I know the voltgae limit for VCC MAIN is almost 4.2 Volt, but when the AMP become dangerous for motherboard??? how many amps vdd main support???

And thanks again for your help sir..

You are my ideal and hope to become like you in the future :))) — AGS
Individual components will get damaged depending on their specified ratings.

So capacitors will blow if you exceed the voltage rating and resistors will blow if you exceed their power rating (Power is equal to Voltage X Current : P=V x I). Coils (this includes ferrite beads, aka. filters) will blow if you exceed their current rating.

As for IC's, they are a combination of all three depending on which part of the internal circuit is affected.

If you look at a schematic, say the iPhone 6, check out the specs on the PMIC page. PP_CPU is spec'd at 7.65A and PP_GPU is spec'd at 3.45A. If you do the power calculations for all of those voltage rails, (plus the BBPMU), you will come to the (maximum) total power consumption of the device. You would then reverse calculate that against the PP_VCC_MAIN voltage to see how much current it actually draws from a battery or DCPS when performing at maximum capacity. It's surprisingly high. — Minho
For fun, let's do some math (P=Vx I):

PP_CPU: 0v95 x 7.65 = 7.2W

PP_GPU: 0v95 x 3.45A = 3.2W

PP_VAR_SOC: 0v95 x 1.8A = 1.7W

PP1V8_SDRAM: 1v8 x .54A = .98W

PP1V2_SDRAM: 1v2 x 1.6A = 1.9W

PP0V95_FIXED_SOC: 0v95 x 3.3A = 3.1W

Just those main rails can draw and dissipate 18W. When you add in all the other PMIC (~5W) and BBPMU (~5W) outputs, it's easy to estimate almost 30W at maximum specs.

Now go back and calculate this from the input voltage of 4.2V and you get

P = V x I or I=P/V

I = ~30W / 4.2V

I = ~7A — Minho

iPhone 7

iPhone 7 Vdd main Short.

1 Risposta

Aggiungi la tua risposta