Yeah, you've done all the things us normal people can to diagnose and fix this problem. Unfortunately, it's starting to look like it may be a board level issue. I've got several sets of iPhone schematics on another machine that I can check tomorrow and see if I have one for the 11 Pro Max. I'm not sure, but @flannelist may know where to find them in order to trace down everywhere the I2C signals for mic2 go; it's possible it extends to another cable that could be the source of the problem. If not, we can at least pin down the chip on the board that's likely to be the issue.
UPDATE 2/27/2023
Located schematics for your phone, here's what I see.
Okay, the MIC2 signal is being handled by U4700; the page is titled Brighton Audio Codec. Signals are connected via J7700. The I2C signals on that connector are labelled I2C1_AP_SCL and I2C1_AP_SDA. Those go to the SOC, U1000 and that's it.
On the way from the connector to the SOC, there are a couple of capacitors going to ground; C7708 on SCL and C7709 on SDA; those are both 56pF 25V. SCL is pin 3 on J7700, and SDA is pin 1. There are also pullup resistors on both lines going to the 1.8V IO power supply; R1430 for SCL and R1431 for SDA. Both are 2.2K 5% 1/32W.
So basically, outside of the power flex, there's a single capacitor and resistor on each of those two I2C lines, and otherwise they go directly from the FPC connector to the SOC. Outside of checking the caps and resistors, there's nothing else there.
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Here's the schematic showing the location of the capacitors; they're right next to the FPC.
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[image|2875642]
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The resistors are over by the SOC. Here's a drawing with them shown.
Yeah, you've done all the things us normal people can to diagnose and fix this problem. Unfortunately, it's starting to look like it may be a board level issue. I've got several sets of iPhone schematics on another machine that I can check tomorrow and see if I have one for the 11 Pro Max. I'm not sure, but @flannelist may know where to find them in order to trace down everywhere the I2C signals for mic2 go; it's possible it extends to another cable that could be the source of the problem. If not, we can at least pin down the chip on the board that's likely to be the issue.
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UPDATE 2/27/2023
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+
Located schematics for your phone, here's what I see.
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+
Okay, the MIC2 signal is being handled by U4700; the page is titled Brighton Audio Codec. Signals are connected via J7700. The I2C signals on that connector are labelled I2C1_AP_SCL and I2C1_AP_SDA. Those go to the SOC, U1000 and that's it.
+
+
On the way from the connector to the SOC, there are a couple of capacitors going to ground; C7708 on SCL and C7709 on SDA; those are both 56pF 25V. SCL is pin 3 on J7700, and SDA is pin 1. There are also pullup resistors on both lines going to the 1.8V IO power supply; R1430 for SCL and R1431 for SDA. Both are 2.2K 5% 1/32W.
+
+
So basically, outside of the power flex, there's a single capacitor and resistor on each of those two I2C lines, and otherwise they go directly from the FPC connector to the SOC. Outside of checking the caps and resistors, there's nothing else there.
Hi Hunter,
Yeah, you've done all the things us normal people can to diagnose and fix this problem. Unfortunately, it's starting to look like it may be a board level issue. I've got several sets of iPhone schematics on another machine that I can check tomorrow and see if I have one for the 11 Pro Max. I'm not sure, but @flannelist may know where to find them in order to trace down everywhere the I2C signals for mic2 go; it's possible it extends to another cable that could be the source of the problem. If not, we can at least pin down the chip on the board that's likely to be the issue.