iPhone 6s front camera not working

[eDigitCom]

History: very clean phone no water damage: All functions working on the phone except the front camera


I noticed however it had got a knock or fall on the top right of the casing (see images) Slight marks on the remainder three sides of the case


The procedure taken to fault find was

• Replaced the proximity sensor and camera with a know good one. It did not solve the issue

• Tried with a know good screen in case some defect in the screen (seen this before) . Did not solve the problem

• Reset all settings Problem still there

• Reset iPhone back to factory setting updated software and still camera faulty

Now has to be hardware problem . Software ruled out


So to me the logic think is that it is a logic board issue


If it is: where do I start fault finding on the logic board

Thanks

[crea2k]

I'm presuming the rear camera works ok ?. I'd check the phone for long screw damage. I'm not sure what lines run under the holes on the 6s but I think on the 6 one of them was camera related. So good to rule that one out.

check the socket for any broken plastic, check none of the pins on the connector are pushed in flush with the connector.

diode mode test the connector

thats the process id follow if you have a known working camera.

[Mohammed]

Like crea2k said...start measuring at it's connector. The connector is the end point for the front cam, so all relevant lines that are needed for it to work are concentrated there. It's always a good strategy to work your way down starting at the endpoint.

[Jessa_the_Professa]

Figure out what lines are required for fcam power and then data. Each line can either be short, open, or the upstream chip that is supposed to produce the power or data is not doing its job.
The easiest way to rule these out is diode mode measurements in the connector. You can also try voltage testing to confirm that power lines are okay (with phone on, camera connected, and cam app open to fcam)

My guess is that this will be an open line under the CPU, but maybe you'll get lucky.

[eDigitCom]

I did quite a few measurements but I could not go further has the women needed her phone for the rest of the weekend. She be bringing it back on Monday for me to completed the testing

I measured all the fCAM siginal on J3100. The measurements taken are attached in a PDF document


I found the signal PP1V8_FCAM_CONN Pin 5 Shorted to ground




Following the signal PP1V8_FCAM_CONN it goes to two caps (See attached) C3103 and C3100. So when I get the phone again I be testing these two caps


I have an in circuit capacitance meter so hopefully I will not have to remove either CAP to find out if one of them are faulty


Question

If one of these CAP's are faulty can you just remove the CAP and not replace it

My thinking is that you would need to replace it with a new one of the same value??

There are a few other measurements that got my attention


INPUTS

TOUCH_TO_PROX_RX_EN_FCAM_CONN Pin 25 Diode Reading infinity ??? Is this a possible open??


I2C_ISP_BI_FCAM_SDA Pin 16 Diode Reading 0.19V IS THIS Normal Seems to be very low??



OUTPUT

MIPI_FCAM_TO_AP_CLK_CONN_N Pin 16 Diode Reading 0.19V Again looks very low but maybe normal


I do not have another iPhone 6s to do a compare at present

Jerry

[crea2k]

The 1.8 line goes to many components, not just the front camera connector, so it may possibly be another cap that's short. If you inject 1volt into the line and check for heat / use freeze spray to find the shorted component that's going to be the best way of finding it. As unless any caps look visually bad you could be there all day.

[eDigitCom]

I agree 1.8 line would go to many components but the PP1V8_FCAM_CONN which is the line that is shorted and following this signal it goes to the 2 caps C3103 and C3100 and the filter FL3100

The short is on the PP1V8_FCAM_CONN side of the board

See attacked schematic image

Would have to also check the line PP1V8 signal and if the short not there then you be looking at PP1V8_FCAM_CONN side of the board

Has all functions are working on the board except the front camera I think if on the other side of FL3102 you have more then the front camera not working?? The signal on the other side of FL3101 goes to J4200 looking at the schematics



I be also concerned with the Input signal to

TOUCH_TO_PROX_RX_EN_FCAM_CONN Pin 25 Diode Reading infinity has this possible open circuit

Jerry

[crea2k]

So you've removed fl3102 to isolate the short to the fcam conn side ?. If so you've only got a choice if two caps it could be. You can either remove them one at a time or I'd just inject 1v into the connector 1.8v line and see which cap gets hot.

[eDigitCom]

No I not remove the coil FL3100 I had to give the women back her phone has she needed it for the weekend. The stage I got to was to take measurements related to FCAM on the connector J310

Why I thinking out loud that the short is on the PP1V8_FCAM_CONN side of the board has it has a direct short to ground

FL3102 has a resistance of 22 ohms and the PP1V8 at the other side of the coil goes directly to another coil FL4205 which has a Resistance of 2K Both these coils are in series Goes also to another coil FL0610 which is an 1K resistance


PP1V8 also goes direct to the BaseBand Chip

So I think if PP1V8 side was shorted would they be more then the Front camera faulty on the phone??

To me if the outher side of the FL3100 was shorted then this is the PP1V8 signal and this goes to locations I think would cause more then the front camera to be faulty??

I may be wrong but going by this I be going more for the 2 caps C3103 and C3100

[crea2k]

If you've not removed the ferrite / filter that part of the circuit is still connected to the rest of the 1.8v circuit. So th short could literally be on any part of the 1.8v circuit.

To test my theory find another 1.8v line that is fed by the same 1.8v line as the camera, see if it's also shorted.

if it is inject 1v into the connector and use freeze spray to find the short.

[eDigitCom]

crea2k can we just forget about finding the fault and take it the short is on the opposite side of FL3101 on the board??

This means the voltage PP1V8 is shorted to ground


PP1V8 goes directly to the following U0600 ( MAUI - USB, JTAG, XTAL), U0900 (Anti-Rollback EEPROM), U1500 (NAND chip), U2000 ( ANTIGUA PMU) and Baseband


Questions

Now has PP1V8 is shorted what is going to happen to the devices I listed above. Are they going to operate normal or are they gong to stop working or maybe half worK

What do you think is going to happen to them??

[Jessa_the_Professa]

Pp1v8 can’t really actually be short to ground. Look at the schematics and tell me what the consequence for the whole phone would be if that was the case. Remember that coils and filters are just wires. 1v8 can have low resistance to ground in a 6s and the phone still works.

My my prediction was that this is going to be a problem under/within CPU. So start there. Use zxw to figure out if your OL reading on the fcam data line is normal or not.

[eDigitCom]

My data lines are OK Jessa

MIPI_FCAM_TO_AP_DATA1_CONN_N Pin 20 Diode Reading 0.61V
MIPI_FCAM_TO_AP_DATA1_CONN_P Pin 18 Diode Reading 0.58V
MIPI_FCAM_TO_AP_DATA0_CONN_P Pin 12 Diode Reading 0.55V
MIPI_FCAM_TO_AP_DATA0_CONN_N Pin 10 Diode Reading 0.56V

It is TOUCH_TO_PROX_RX_EN_FCAM_CONN Pin 25 on J3100 that is open circuirt


This an active high enable line for the FCAM An Open circuit produces a high so the camera will be enabled


But not be correct to have it open circuit


PP1V8_FCAM_CONN is shorted so no power to the FCAM so cannot turn on

[Sly]

Hi eDigitCom,
Nice work with the troubleshooting steps in the beginning to rule out other problems than the board, and I like how you've organised your question.

Let me point out the C3101 is part of PP1V2_FCAM_VCORE_CONN, and so is FL3102, but c3100 is part is PP1V8_FCAM_CONN.

Those are two different lines, but you had mentioned all those components as part of PP1V8_FCAM_CONN.

Lets clarifying this by taking a diode measurement on the J3100
Pin 5
Pin 6
Pin 8
Red pin on Ground, Black pin of the fpc pin.

Good Luck!

[eDigitCom]

Well spotted about FL3102 This was a typo error I will change it. I should have written FL3100


See attacjed

I measured pin 5 (short to ground) and pin 6 this is OK see the above PDF I uploaded to see DIODE mode tested

Pin 8 on J3100 is not connected (not used)