all PP_LDO lines missing

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iPhone xr

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Mateusz Lacki @lacek

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Postado: 30 de out de 2017

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all PP_LDO lines missing

Hi,

I have an iPhone 6 board which seems to have all the PP_LDO lines missing (all of them). They are not shorted, as the resistance to ground reads in megaohms, but when the board is powered on (screen shows restore with iPhone) the lines are absent.

I want to ask if this is normal when the phone is in the DFU mode? More or less everything is disconnected from the logic board.

Unfortunately I do not have a known good board to check that.

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most of these lines seem to lead to U_PMICRF so i would check around that area

31 de out de 2017 por daniel

This is the point. I want to distinguish between faulty baseband and faulty baseband PMIC. On the other hand it might be that these lines are software-activated and it is not that weird that these lines are missing.

31 de out de 2017 por Mateusz Lacki

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Minho @refectio

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Those lines should be active when you power up the logic board. Have you also checked the VREG_SMPS1 (2/3/4) lines to see if they are generating any output voltages?

I would start by confirming that VBATT_S1 (2/3/4) are present and not shorted (they shouldn't be because they are directly connected to VCC_MAIN). If none or most of the outputs voltages are present, then I would suspect the PMICRF first. Be careful when you replace it because there is a trailer park's worth of caps right next to it and when they start shifting around, they tend to bridge easily and it's hard to separate them.

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Does the DFU mode play a role here?

31 de out de 2017 por Mateusz Lacki

I can't say for certain...I'd have to check that condition.

31 de out de 2017 por Minho

Anyway VBATT_S1 (2/3/4) shows 4V to ground. VREG SMPS1 (2,3,4) are all missing. so it seems its likely a baseband PMIC ?

31 de out de 2017 por Mateusz Lacki

Yeah, that's my thinking.

31 de out de 2017 por Minho

I have also checked now that the VREG_SMPS1 (2,3,4) are missing during my attempted restore through iTunes (i soldered jumper test wires to the capacitors and monitored those lines on the oscilloscope - flat zero all the time)

9 de nov de 2017 por Mateusz Lacki

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most of these lines seem to lead to U_PMICRF so i would check around that area — daniel
This is the point. I want to distinguish between faulty baseband and faulty baseband PMIC. On the other hand it might be that these lines are software-activated and it is not that weird that these lines are missing. — Mateusz Lacki
Anyway VBATT_S1 (2/3/4) shows 4V to ground. VREG SMPS1 (2,3,4) are all missing. so it seems its likely a baseband PMIC ? — Mateusz Lacki
I have also checked now that the VREG_SMPS1 (2,3,4) are missing during my attempted restore through iTunes (i soldered jumper test wires to the capacitors and monitored those lines on the oscilloscope - flat zero all the time) — Mateusz Lacki

iPhone xr

all PP_LDO lines missing

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