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820-00928 External USB mouse & keyboard not working

Rlab

Rlab

Member
Hi guys,
I'm working on a Macbook pro 15 inch 2017 A1707 that fully works but external USB mouse and keyboard.
all the USB-C ports work, charging, Hard Disk & HDMI.
We have tried safe mode, external HD with different OS versions & different USB-C original adapters.
Magic mouse works fine as well as the internal keyboard and trackpad.

We tried USB mouse and keyboard with and without cable but none of them work.
the cable mouse turns on the light at the bottom but cable keyboard doesn't have any sign of getting power.

This is the 3 time this mac comes to us.
The first 2 times came because it wasn't turning on, the first time we needed to replace two USB-C chips
and the second time we needed to replace 3 USB-C chips.

Now everything works fine except for the external Mouse & Keyboard.

it has no pending Catalina updates and I couldn't fin any software issue related to the M&K.

What could be the problem on the motherboard?
what power rail should be present to make external USB M&K work?


Many thanks !
 
2informaticos

2informaticos

Administrator
Staff member
Seems that USB 3 devices are working; supposing you've tested external HDD with USB 3 connection.
Should be a problem with USB 2.0 lines.
However, test first with another USB-C hub.
 
Last edited:
Rlab

Rlab

Member
We did try a couple of USB-C hubs, new ones and from a working mac.
where should I start to check the USB 2.0 lines?
 
2informaticos

2informaticos

Administrator
Staff member
J3300 and JB500 have two USB2 pairs (TOP/BOT) for each port.
Check diode mode on these lines.
CD3215 chips stay between PCH and USB 2.0 inputs.
Also check diode mode on CD3215 outputs; L3100/200 and LB300/400.
 
Rlab

Rlab

Member
J3300
USBC_XB_USB_TOP_P 1.31
USBC_XB_USB_TOP_N 0.89
USBC_XB_USB_BOT_P OL
USBC_XB_USB_BOT_N OL

USBC_XA_USB_DBG_BOT_P OL
USBC_XA_USB_DBG_BOT_N OL
USBC_XA_USB_DBG_TOP_P OL
USBC_XA_USB_DBG_TOP_N OL


JB500
USBC_TB_USB_TOP_P 1.92
USBC_TB_USB_TOP_N 0.00
USBC_TB_USB_BOT_P 0.75
USBC_TB_USB_BOT_N 0.75

USBC_TA_USB_TOP_P OL
USBC_TA_USB_TOP_N 0.80
USBC_TA_USB_BOT_P OL
USBC_TA_USB_BOT_N OL

L3000 0.54
1.- 0.54 4.- 0.54
2.- 0.54 3.- 0.54

L3200 0.50
1.- 0.54 4.- 0.54
2.- 0.54 3.- 0.54

LB300
1.- 0.53 4.- 0.53
2.- 0.53 3.- 0.53

LB400
1.- 0.53 4.- 0.53
2.- 0.00 3.- 0.00
 
Rlab

Rlab

Member
So... I have a short on USB_UPC_TB_F_N (I removed RB253)
I will replace UB400 and will update (TOP/BOT) diode mode values as well as L3000/200 and LB300/400
 
Rlab

Rlab

Member
Yes, you are right, I did check like that the diode mode values, I'm using a fluke 107.
Once I replaced UB400 I got the following differences in values:

JB500
USBC_TB_USB_TOP_P OL
USBC_TB_USB_TOP_N OL
USBC_TB_USB_BOT_P OL
USBC_TB_USB_BOT_N OL

LB400
1.- 0.53 4.- 0.53
2.- 0.53 3.- 0.53

I still don't have external M&K..

I checked diode mode values on a working board and it looks like with my multimeter all the (TOP/BOT) lines should be OL.
can you please confirm what diode mode values should I get on these lines?

If OL values are correct it could be that I need to replace another 2 CD3215 chips..
 
Last edited:
Rlab

Rlab

Member
Its working !!!!!

To recap...

UB400 was shorting USB_UPC_TB_F_N that's why LB400 had 0.00V on diode mode in pins 2 & 3.

Testing again the USB M&K, we found external mouse activity only in one USB-C hub by connecting the adapter upside down which lead us to test once again with new USB-C hubs and BOOOOM ! external M&K working like a charm !

2informaticos thank you very very much!
 
Last edited:
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