820 - 3437 - B Macbook Air intermittent power related issues

[Maxibon]

I have a Macbook Air 820 - 3437 - B

The Macbook has had issues booting but once I disconnect and reconnect the battery it's fine.

I has also had an issue where after shutdown, if you press the power button, it won't button unless you hold it in.

It has 'XYZ' percentage while plugged in, and once you disconnect the DC it can change, ie, from 75% plugged in to 69%.

Once you plug it back in it may go back to 'XYZ' percentage or stay where it's at. Very strange.

Custom says they have issues booting it all the time, however I do.

These are the only symptoms I can find - unsure of previous repairs, so is customer.

Thanks, Max!

 

[2informaticos]

"The Macbook has had issues booting but once I disconnect and reconnect the battery it's fine."
You did SMC reset in fact; seems that helped.

You should test known good working battery.

 

[piernov]

And another touchpad/keyboard.

 

[Maxibon]

Hey guys!

I've tried a known good battery, same issue, except now I'm getting more of a hint to what's going on.

I'm getting fan spin for 5 seconds then stop, that on repeat over and over with no boot, this is what the customer was complaining about and what I'm seeing now.

Does that hint to anything else?

I'll try another keyboard and track pad.

Thanks.

 

[2informaticos]

If new trackpad board/flex doesn't help, try known good BIOS.

SMC_ONOFF_L drops from 3V to 0V when pressing power button?

 

[Maxibon]

Thanks for your reply.

I've switched out the keyboard and mouse, still same thing.

Do I need Medusa to swap out bios or can I just transfer U6100 from one board to another?

after measuring SMC_ONOFF_L it sits at 3.4V the whole time.

While it's having issues not booting the fan spins for 5 seconds and then stops.

If I continue to hold in the power button eventually it'll turn on, always syncs turning on with a fan spin.

Does any of this help - I would prefer if it wasn't intermittent lol

 

[2informaticos]

3437 board starts in 3rd fan spin attempt, as normal behaviour.
However, I saw this board model starting at first attempt, like 00165; working good, without noted any issue.

Does SMC_ONOFF_L drop when you press power button?
If not, try using R5115/16 pads instead.

 

[Maxibon]

Thanks again for your reply.

I understand this board will fan spin 3 times before boot - however - this isn't always the case.

Sometimes this board will fan spin like normal. but just continue to do so, until I press and hold the power button and eventually it'll boot.

I measured SMC_ONOFF_L and it appears to sit at 3.4V It will only drop to 0v when it intermittently boots proper.

When you say try using R5115/16 pads, do you mean to measure? what am I looking for?

 

[2informaticos]

R5115/16 pads can be used to simulate power button.
SMC_ONOFF_L MUST drop to 0V when power button is pressed (or simulated).

 

[Maxibon]

When pressing the power button, while measuring SMC_ONOFF_L - it drops to .4v - it still boots when only dropping to .4v

I hope this helps. :/

Max

 

[2informaticos]

Did you try new BIOS, known good?

 

[Maxibon]

Not yet.

I asked if " Do I need Medusa to swap out bios or can I just transfer U6100 from one board to another?"

Sorry wasn't sure.

Hope you can let me know.

Thanks.

 

[2informaticos]

If you swap with KNOWN GOOD WORKING BIOS chip from other board, it should boot; if is BIOS issue.
But you finally need to clean ME region, as the other board has a DIRTY ME region for your PCH.