820-00138 I/O board USB problem

Narek

Member
This one is really strange. I got A1398 which is working perfectly fine except right side USB port, which is working partially - it recognises external flash drives, USB mouses or even boots and works from external drive OS, but the problem is, that it doesn't recognise iPhone at all. AMP meter shows 5V but 0,03-0,05A of drain when phone is connected (it won't recognise phone with AMP meter disconnected too). If I connect 2,5" HDD over adapter, it takes 0,79A, then drops to 0,12A and doesn't recognise it. But if I connect the same drive without AMP meter drive is recognised and works OK. I have already replaced I/O board and both flex cables, but with no success. Connectors on motherboard look perfect, no corrossion or damage. Other side USB port works completely fine with all devices I connect to it. I thought it could be power problem, but it keeps 5V stable on board. Maybe it's PCH protocol problem?
 

Narek

Member
It raises to 3,3V when computer turns on and stays like that all the time, no matter if I connect devices to USB port.
 
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2informaticos

Administrator
Staff member
So USB overcurrent is not triggered.
Can you check with similar machine the behaviour of right USB port?
 

Narek

Member
On the similar machine right port works normally, it detects and charges iPhone (or other phones). USB_EXTB_OC_L line is stable 3,3V and doesn't change if I connect USB device.
 

2informaticos

Administrator
Staff member
Check C9501/02.
Also check diode mode to ground on USB3_EXTB data lines.
Maybe right port only works in USB 2.0 mode.
 

Narek

Member
C9501/02 are not shorted. Pin 2 on both caps reads OL, pin 1 reads 0,335V in diode mode. Traces are OK too.

data lines diode mode readings (I/O board disconnected):

USB3_EXTB_R2D_N - OL
USB3_EXTB_R2D_P - OL

USB3_EXTB_R2R_N - 0,323
USB3_EXTB_R2R_P - 0,323

USB_EXTB_N - 0,367
USB_EXTB_P - 0,369

data lines diode mode readings (I/O board connected):

USB3_EXTB_R2D_N - OL
USB3_EXTB_R2D_P - OL

USB3_EXTB_R2R_N - 0,323
USB3_EXTB_R2R_P - 0,323

USB_EXTB_N - 0,367
USB_EXTB_P - 0,364
 
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