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820-4924-a wont turn on

estelanim416

estelanim416

Member
Hi,
Received the MacBook in for non-responsive keyboard. Upon inspection, Unit was fully working with the external keyboard. It would accept keyboard shortcuts at boot but nothing once we were in os. We found quite a few places with liquid residue. Put it through cleanup in crest ultrasonic cleaner. It will not power on now, no chime, no backlight no spin. I have 3rd party charger that goes green when plugged.
Had a look under a microscope and nothing pops out.
Please advise

Kind regards,
 
2informaticos

2informaticos

Administrator
Staff member
Remove keyboard and connect magsafe; does it turn on?

Be aware of ultrasonic cleaners w/o sweep function.
Change the board position every 30s and do not let it more than 10min total in the bath.

Post some voltages in the U7100 and Q7010 areas.
Check if D7010 is still in place.
 
estelanim416

estelanim416

Member
I tried with speaker and fan only. I might have messed it up as it was definitely longer than 10 min but my crest has a sweeping function, its the recommended one for those jobs. D7010 present. C7101 is 5.45v C7100 same C7105 16.45V, C7122 14.33v, C7120 0v those are around U7100.
C7012 8.15v ( i am guessing the component here as my board view is a bit different to the board I have) that's the only cap I found around the Q7010.
 
Last edited:
J

JohnB8812

New member
Yeah post voltages for PPVRTC_G3H, PP5v_S5, PP3v3_S5, PP3v3_SUS, and PP5v_S4. If you have all of those, then check for PP5v_S3 like 2informaticos asked for
 
estelanim416

estelanim416

Member
All 3.3 lines have 3.3v
I am getting 4.9v on c7505 that's part of PP5V_S5, but 0v on two components on PP5v_S4, PP5v_S3 also 0v

Those checks I do with only power connected, The light on the charger switches from green to amber and back to green in 10 sec intervals
 
2informaticos

2informaticos

Administrator
Staff member
"5V_S3 pulsing at least?"
You can also check if PM_SLP_S4_L pulse once, or every 5sec.
If not, post SMC_ADAPTER_EN, PM_BATLOW_L, PM_RSMRST_L.

Does PM_PWRBTN_L react if you trigger SMC_ONOFF_L?
If not, check all PCH's RTC signal, and 32KHz clock from U1900.
 
estelanim416

estelanim416

Member
Unfortunately, I don't have an oscilloscope :( I believe I would need it to see the pulsing?
Just a multimeter to use
I am not totally new but still learning.
The multimeter doesn't pick up any voltage
SMC_ADAPTER_EN 3.37v
PM_BATLOW_L 0.03v
PM_RSMRST_L 3.28v

I am hoping it is still possible to assess the board without the oscilloscope

Not sure how to trigger the SMC_ONOFF_L, it seems to be on 3.4v all the time unless I am doing something wrong
PM_PWRBTN_L also constantly on 3.4v
 
2informaticos

2informaticos

Administrator
Staff member
"Not sure how to trigger the SMC_ONOFF_L, it seems to be on 3.4v all the time"
Force it 1s to ground, like pressing power button; use R5115/16 pads.

"PM_BATLOW_L 0.03v"
PCH will not start Power On Sequence then...
Did you try original 85W charger?
 
estelanim416

estelanim416

Member
Thanks for all the help

After triggering, PM_PWRBTN_L jumped from 3.4v to 2.6v and back to 3.4v
I am testing without the battery being plugged in - not sure if that matters
Just tried plugging it in with an original 45w charger and battery/fan/speaker. Got a chime but no fan spin so I disconnected it - not sure if that helps
 
2informaticos

2informaticos

Administrator
Staff member
The fan starts later on this board, when something gets hot...
Do you have USB activity?
Also check for image, even if no backlight present.
 
J

JohnB8812

New member
Yeah the fan doesn't spin on this model until the CPU heats up. Light on USB mouse with the chime? If so exactly what 2informaticos said check for image.
 
estelanim416

estelanim416

Member
Ok, it started up, somehow it starts up now. Get the picture, black screen "question mark folder", doesn't see the disk for some reason, the keyboard also doesn't work. I tried the ssd in another mac and its booting and loading os so it must be something to do with the motherboard. Should I start another topic? or can I continue here?
 
2informaticos

2informaticos

Administrator
Staff member
Continue here...
Keyboard/trackpad work in boot menu and don't work under OSX?
Check traces around SSD connector; post voltages (with SSD inserted) for U3740.
 
estelanim416

estelanim416

Member
the U3740 pin1 - 3.4v, pin 2 - 0v, pin 8 - 0.08v, (I checked those when plugged but not on)
The keyboard seems to be completely unresponsive now, apart of the power button, no trackpad either
 
estelanim416

estelanim416

Member
Sorry, I could find the J3470, neither on the schematics nor in BoardView, I am obviously missing something. I had to plug in the external keyboard to Alt boot, internal keyboard didn't let me do that
 
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