Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Laptops, Tablets, and Mobile Devices
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 07-14-2021, 05:58 AM   #1
marce002
Senior Member
 
Join Date: May 2018
City & State: martinez
My Country: Argentina
I'm a: Knowledge Seeker
Posts: 134
Default A1286 2915 does not power from BUTTON but works!

Hello

Im playing with my honor here.... cant figure out this!!


Working fine a1286 (2011) macbook 820-2915-A....

I needed to test a keyboard from another (identical) macbook ..
The keyboard did not work at all, maybe was bad or incorrect version. no labels at all...so i dont know....

then, reinstalled everything back to the good macbook , but now does not power on from power button, only from a short to GND at R5016... rest is normal...

I spent day working on this and this is ridiculous,

measured continuity from pin5 keyboard connector and was interrupted in his way to the other side: R5710 pin2

so made a jumper and thought would be ok....but

Still not powering on , but 3.33v present at R5710 both sides!!

what is wrong?

the same laptop powers on well with another motherboard, so it is not a keyboard issue.

What else can I try? some pictures as reference and schematics provided.

thanks in advance






Attached Files
File Type: rar A1286-2915b.rar (2.01 MB, 0 views)
marce002 is offline   Reply With Quote
Old 07-14-2021, 06:30 AM   #2
mon2
Badcaps Veteran
 
mon2's Avatar
 
Join Date: Dec 2019
City & State: Windsor, Ontario
My Country: Canada
Line Voltage: 110VAC
I'm a: Knowledge Seeker
Posts: 1,208
Default Re: A1286 2915 does not power from BUTTON but works!

1) confirm that R5710 is a 1k resistor.

2) remove the keyboard. Short the logic board Power Button pads @ R5016. Does this work to turn the logic board ON / OFF ?

3) Then do the same short @ R5710, Pin # 1.
Does this work to turn the logic board ON / OFF ?

4) Then do the same short @ R5710, Pin # 2 (with keyboard still out).
Does this work to turn the logic board ON / OFF ?

The +3v3 on SMC_ONOFF_L is due to the 10k pull-up @ R5070.

If the above manual bypass methods work then suspecting a connector / contact issue @ pin # 5 of J5713.

If you have enough hands, consider to probe pin # 2 of R5710 while pressing down on the keyboard on/off button to confirm it indeed goes low during a press.

Cleaned the keyboard cable contacts with alcohol ?
mon2 is offline   Reply With Quote
Old 07-14-2021, 06:32 AM   #3
piernov
Moderator
 
Join Date: Jan 2016
City & State: Valbonne, 06
My Country: France
I'm a: Knowledge Seeker
Posts: 3,327
Default Re: A1286 2915 does not power from BUTTON but works!

If machine turns on when shorting pin 5 of keyboard connector to ground but not when pressing power button on the keyboard, then keyboard connector or keyboard flex is bad.
__________________
OpenBoardview http://openboardview.org
piernov is offline   Reply With Quote
Old 07-14-2021, 04:51 PM   #4
marce002
Senior Member
 
Join Date: May 2018
City & State: martinez
My Country: Argentina
I'm a: Knowledge Seeker
Posts: 134
Default Re: A1286 2915 does not power from BUTTON but works!

Quote:
Originally Posted by mon2 View Post

1) confirm that R5710 is a 1k resistor.
yes it is

2) remove the keyboard. Short the logic board Power Button pads @ R5016. Does this work to turn the logic board ON / OFF ?

yes it powers up


3) Then do the same short @ R5710, Pin # 1.
Does this work to turn the logic board ON / OFF ?

yes it powers up too

4) Then do the same short @ R5710, Pin # 2 (with keyboard still out).
Does this work to turn the logic board ON / OFF ?

yes it powers up too

The +3v3 on SMC_ONOFF_L is due to the 10k pull-up @ R5070.

If the above manual bypass methods work then suspecting a connector / contact issue @ pin # 5 of J5713.

If you have enough hands, consider to probe pin # 2 of R5710 while pressing down on the keyboard on/off button to confirm it indeed goes low during a press.

it goes down yes!! after my jumper (see red line in my above picture)... that is the strange thing here. also the same keyboard connector works with another mother so it is a mother issue

Cleaned the keyboard cable contacts with alcohol ?

yes did it before.. no results.

Last edited by marce002; 07-14-2021 at 04:56 PM..
marce002 is offline   Reply With Quote
Old 07-14-2021, 04:54 PM   #5
marce002
Senior Member
 
Join Date: May 2018
City & State: martinez
My Country: Argentina
I'm a: Knowledge Seeker
Posts: 134
Default Re: A1286 2915 does not power from BUTTON but works!

Quote:
Originally Posted by piernov View Post
If machine turns on when shorting pin 5 of keyboard connector to ground but not when pressing power button on the keyboard, then keyboard connector or keyboard flex is bad.
nop because same keyboard/connector/button works perfect with another motherboard.
marce002 is offline   Reply With Quote
Old 07-14-2021, 07:02 PM   #6
mon2
Badcaps Veteran
 
mon2's Avatar
 
Join Date: Dec 2019
City & State: Windsor, Ontario
My Country: Canada
Line Voltage: 110VAC
I'm a: Knowledge Seeker
Posts: 1,208
Default Re: A1286 2915 does not power from BUTTON but works!

1) locate the ground pad on the keyboard flex cable.

2) power down and work with the keyboard only.

3) meter in resistance mode (200 ohms). Red meter lead on pin #5 if keyboard cable, black on the ground pad of the keyboard cable. Press the on/off button. Do you see pin #5 short to the ground pad of the cable?

4) repeat with the keyboard attached to the logic board. Are the results the same?
mon2 is offline   Reply With Quote
Old 07-15-2021, 05:24 PM   #7
marce002
Senior Member
 
Join Date: May 2018
City & State: martinez
My Country: Argentina
I'm a: Knowledge Seeker
Posts: 134
Default Re: A1286 2915 does not power from BUTTON but works!

Quote:
Originally Posted by mon2 View Post

1) locate the ground pad on the keyboard flex cable.

2) power down and work with the keyboard only.

3) meter in resistance mode (200 ohms). Red meter lead on pin #5 if keyboard cable, black on the ground pad of the keyboard cable. Press the on/off button. Do you see pin #5 short to the ground pad of the cable?

4) repeat with the keyboard attached to the logic board. Are the results the same?


with keyb connected:

3* no battery no plugged in, keyboard connected , black on pin 29 GND, and red in pin 5 goes from 300/200kohm down to aprox 100kohm .. restarting this measurement goes to 200k again and down to around 130k....weird
button pressed messed up things , when pressed down to 8kohm , when unpressed goes up to 2 or 3 Mohms.... very noisy numbers, not constant not fixed values, always moving but great difference in res pressed and unpressed...

with NO keyb connected:


OL when not pressed and 0,4Kohm when pressed... constant values almost
marce002 is offline   Reply With Quote
Old 07-15-2021, 05:49 PM   #8
mon2
Badcaps Veteran
 
mon2's Avatar
 
Join Date: Dec 2019
City & State: Windsor, Ontario
My Country: Canada
Line Voltage: 110VAC
I'm a: Knowledge Seeker
Posts: 1,208
Default Re: A1286 2915 does not power from BUTTON but works!

Are you 100% sure this keyboard is for use with this logic board?

The pull down is not strong enough with this keyboard to perform the on/off function. The resistance is just too high. If you are really in a pinch and have to use this keyboard, you can try to apply another resistor to ground on this pad. The effect we want is that when you press the on/off button, the resistance from this keyboard in parallel with the external resistor will allow for the function. It is only an idea but should work. The proper solution is to find a better keyboard or a new one. The above idea will require some trial and error.


Test with another keyboard and check the on/off pad using the same method. Once you can get the resistance down, it will work.
mon2 is offline   Reply With Quote
Old 07-15-2021, 06:15 PM   #9
mon2
Badcaps Veteran
 
mon2's Avatar
 
Join Date: Dec 2019
City & State: Windsor, Ontario
My Country: Canada
Line Voltage: 110VAC
I'm a: Knowledge Seeker
Posts: 1,208
Default Re: A1286 2915 does not power from BUTTON but works!

To clarify on your testing...

remove the keyboard off the logic board.

Using the keyboard (ONLY) - check the resistance on the ON/OFF pad (red meter lead) and ground on the keyboard cable (black meter lead). This test has nothing to do with the logic board - just the keyboard & meter will be used.

Then press the ON/OFF button on the keyboard - what are your resistance readings?

Concluding so far that your keyboard is defective or not the proper model for this logic board.

The defect could be as simple as some liquid inside the membrane / closure of the button(s).
mon2 is offline   Reply With Quote
Old 07-15-2021, 07:25 PM   #10
marce002
Senior Member
 
Join Date: May 2018
City & State: martinez
My Country: Argentina
I'm a: Knowledge Seeker
Posts: 134
Default Re: A1286 2915 does not power from BUTTON but works!

Thanks i will try to lower the resistor and comme t. The keyboard was ok and original since it is from the first macbook... remember this happened after commecting the bad keyboard to the good system as i have stated in my first post.
Also remember that swaping motherboards the system starts ok with that same keyboard and same button.....
It make sense to lower the res... i will test that.

Last edited by marce002; 07-15-2021 at 07:27 PM..
marce002 is offline   Reply With Quote
Old 07-16-2021, 11:22 AM   #11
marce002
Senior Member
 
Join Date: May 2018
City & State: martinez
My Country: Argentina
I'm a: Knowledge Seeker
Posts: 134
Default Re: A1286 2915 does not power from BUTTON but works!

Yes!!! 10k Parallel resistor did the trick. Thanks mom2 ..thanks to all.
marce002 is offline   Reply With Quote
Old 07-16-2021, 11:49 AM   #12
mon2
Badcaps Veteran
 
mon2's Avatar
 
Join Date: Dec 2019
City & State: Windsor, Ontario
My Country: Canada
Line Voltage: 110VAC
I'm a: Knowledge Seeker
Posts: 1,208
Default Re: A1286 2915 does not power from BUTTON but works!

Well done
mon2 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2021
Powered by vBulletin ®
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 01:36 PM.
Did you find this forum helpful?