No power button - Mac Air 2013

[jpadie]

Any thoughts on power button not working? Tried two keyboards and two batteries (one known good of each) .

No obvious corrosion on trackpad . Continuity in ribbon cable seems fine. No obvious corrosion there either. Connector on board is fine too.

Board powers on with charger . Recognises battery.

Thanks!

 

[dukefawks]

Measure SMC_ONOFF and see if it does anything when pressing the button. Manually short the pads to see if it works, R5115/5116.

 

[jpadie]

Resurrecting this thread, on R5115/6 I have the expected 3.42v/gnd on the pins. plugging in a keyboard and pressing the power button shows no change on SMC_onoff. is this a sure sign of a dead kb?

manually shorting the pads caused a reboot.

the board history is water (wine) damage around the lcd connector and RTC. Board spins up and performs fine, just no power button ….

it did also have a bad camera. I have not tested the replacement yet but I guess this could be a faulty SMC too?

 

[2informaticos]

Rebuild broken trace from keyboard connector and SMC_ONOFF_L line.
Keyboard connector could also be damaged too...

 

[jpadie]

Thanks

The trace are fine. Each pin of the flex cable has continuity to its pair too .
This is the second keyboard too....
kB connector is visually good under a microscope.

 

[jpadie]

I just tried the board in a new chassis and it worked fine. so either a keyboard problem or flex cable or trackpad. will narrow it down tomorrow.

 

[2informaticos]

Trackpad is not involved here.
Power button has separate trace to SMC_ONOFF_L line.
Check continuity from keybard connector to SMC_ONOFF_L.
If OK, you have bad contact on the connector, or bad flex.
I was thinking you already tried another flex...

 

[jpadie]

how can that be right? the keyboard connects into the trackpad, and the trackpad connects to the board. so if there is an issue on the trackpad board then that will affect the keyboard comms.

as above - connector to smc_onoff_L is fine. cable tests fine too and of course I have tried others. but sod's law can always mean that the replacement is broken... the keyboard being tested is brand new and bought because the last keyboard exhibited the problem of no-power-button.

I really think the trackpad is the most likely candidate. but as above, I will do some exclusion tests to work out which part to re-order.

thanks for the engagement. I will post back the conclusion tomorrow.

 

[2informaticos]

Power button has separate line from keyboard through the trackpad board untill IPD flex.
I meant trackpad electric circuitry is not involved.
I now realized you tested the board in other chassis and it is OK.
My mistake, I understood the opposite...

So check continuity from SMC_ONOFF_L of IPD flex to the keyboard connector on the trackpad.
I suppose corrosion on the corresponding trace, or one of its connectors.
In this case is maybe better to replace trackpad entirely.

 

[jpadie]

it was the trackpad in the end. flex cable was fine. keyboard fine.​

no noticeable corrosion in the trackpad circuitry. but evidently something was wrong as the ONOFF line was not being brought low.

but this is the board that keeps on giving! I've now tried two other trackpads in the device. Both allow the ONOFF line to be pulled low but on both the trackpad chip behind the connector to the board gets instantly extremely hot. They also stop the laptop booting (power resets continually, or the boot gets almost to the end and then shuts off, no chime. Both these are from other chassis on my bench so it is possible that both are bust. But before I order new ones, what's the view of people here? fan spin, chime, boot and no heat when the trackpad without the working power circuitry gets plugged in!

are there schematics and boardviews for the trackpads? there is no evident corrosion on any of the trackpads, nor any signs of damage. and although I have no reason to doubt you, 2informaticos, I cannot find any pins that have continuity between the flex connector to the board and the flex connector to the keyboard. So what pins should be connected for the power button? ​