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820-00239 works only with keyboard disconnected

2informaticos

2informaticos

Administrator
Staff member
SMC_LSOC_RST_L must be always high.
Check R5258, U5256 and traces.
Can also be a problem underneath keyboard connector.

SMC_ONOFF_L is steady 3V?
 
N

Narek

Member
SMC_LSOC_RST_L is always 3,3v, no matter with or without keyboard connected.
SMC_ONOFF_L steady 3,4v
All voltages on U5256 are present, only SMC_4FINGERS_RST is 0v

Keyboard connector is well soldered, on the other side of the boar there are only Q6000/Q6050 with some caps and resistos, they all look and measure good.
 
2informaticos

2informaticos

Administrator
Staff member
" SMC_LSCO_RST_L - 0,707v (when board turned on gets 3,3v both with and without keyboard)
----------------------
SMC_LSOC_RST_L is always 3,3v, no matter with or without keyboard connected"
Can you clarify, please???
Of course, interests this signal when board doesn't boot.
 
2informaticos

2informaticos

Administrator
Staff member
"only SMC_4FINGERS_RST is 0v"
Is correct; note that it doesn't have the "_L" on its name.

Keyboard data lines go to trackpad, J4500 -> J4501.
Only fans connect directly with the MLB.

Trackpad flex/board changed?
 
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N

Narek

Member
The whole topcase was replaced by Apple. I’ve asked them for details which parts they left there from old topcase and they have replaced everything except board, screws and Touch ID, so trackpad flex and board were replaced too.
 
2informaticos

2informaticos

Administrator
Staff member
Keyboard matrix information (key pressed) comes through I2C bus (J4500) and goes to trackpad (J4501).
Finaly, keyboard information goes to PCH via SPI, along with trackpad information.
 
N

Narek

Member
Exactly, it was restarting all the time during boot. But today for example in most cases board doesn’t even try to start with keyboard connected.
 
2informaticos

2informaticos

Administrator
Staff member
Then the problem is not with keyboard matrix.
Should be something related with the fans, or keyboard backlight circuit.
Are you sure Apple changed all the mentioned things?
I don't understand why they changed all these things and returned machine as non working, really strange.

Just be sure SMC_LSOC_RST_L stays high.
 
N

Narek

Member
2informaticos said:
Are you sure Apple changed all the mentioned things?
Click to expand...

I'm sure they have replaced complete topcase. Only things they left are motherboard, Touch ID, display and screws. They have replaced topcase under keyboard replacement program, but as computer already doesn't have warranty, they left it like that and said, that motherboard needs to be replaced too.

2informaticos said:
Should be something related with the fans, or keyboard backlight circuit.
Click to expand...

I have disconnected both fans from keyboard and removed Q6000 and Q6050 - no changes. Will take a look at backlight circuit,

2informaticos said:
Just be sure SMC_LSOC_RST_L stays high.
Click to expand...

It's always hight, 3,4v.
 
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N

Narek

Member
I started isolating pins in J4500 with capton tape and discovered, that when i isolate upper row of pins in connector, board boots fine. Then I isolated left/right half of pins, it turned out, that with right side of upper pins isolated board boots fine. I started isolating each pin separately and narrowed it down to KBD_I2C_SDA. With this pin isolated (no matter on J4500 or J4501) and both keyboard and trackpad flex connected board boots fine, but obviously keyboard doesn't work. With only keyboard flex connected board doesn't start at all.
 
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N

Narek

Member
@2informaticos, in meanwhile got the same mac model for repair with another issue and used occasion to swap the boards. This keboard with other board works fine. I put the board to another topcase with fully working keyboard and keyboard doesn't work. So the problemis related to mainboard itself..
 
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