Apple MacBook A1181 power button problem / magsafe green light issue

Hello,

This is the result of a small trouble shoot I've done by chance when I found a broken MacBook A1181 (Intel duo type) in the recycling.

 

The first symptoms were different, first - the power adapter magsafe connector light not turning on ( green ) at all. Once, finally it did turn on - green- then I press the power button, it turned on but no operating system.

The machine was missing the hard drive, obviously taken out for "data protection". Also the battery was probably recycled so I only had a charger to try to turn the MacBook on.

I put in a used hdd and install windows just because I did not had any mac os disk at hand. Everything was working fine... I turned off and the power button refused to work again after!!

I removed the magsafe and plugged back in, not even the green light came on - weird!

Next day, it turned on but did not stay long, the MacBook A1181 turned off by itself - weird.

I removed the top half ( keyboard ) and disconnected from the motherboard - then I found interesting that all the bad symptoms were gone, magsafe light comes green right away, it powers on and stays on with no problem. I used the two small pads beside the fan case ( look for a small power symbol ) short them and it will power on.

I put the cover back and reconnected the small connector, again was still not working.

The price of a new top ( keyboard ) part is ridiculous, only to fix this power button problem.

Now comes the serious staff. The power button signal can be read on the track pad, see the picture below:

Under the track pad, power on signal

On a normal power button from a MacBook A1181, the test point measure 3.4V in standby and 0V when the power button is depressed.

My A1181 power button voltage was about 1.7V! This was measured when I was connecting the magsafe connector and there was no green light coming on. Why? It's time for some research on the web.

I found the A1181 MacBook schematics on the web (elektrotanya.com- search for A1181) here is the page with the power controller that turns on the motherboard in the A1181:
 

 

That signal comes from the keyboard connector, here is the pic:

A1181 keyboard connector

 

Shorting the pin 1 to GND does the same thing, turns on the laptop. For some reason, the voltage on that SMC_ONOFF signal never goes up to 3.4V while the keyboard is connected.

To actually do the fix you have to be careful, only work on the disassembled and disconnected keyboard, otherwise you will break your motherboard.

DISCLAIMER: You do this at your own risk, I am not responsible for any damage done to your laptop or data, you have been warned.

The power button develops a lower internal resistance that defeats the weak pull up from the power controller, thus the voltage drops to 1.7V. I tried a manual pull up to 3.4V, using a 10K resistor, it works, but the voltage still goes only up to 2.7V, not fully 3.4V.

These are steps I have done to try to fix the issue:

So, you have to have this in front of you:

Keyboard A1181 back

Zoomed track pad back

 

This is the most difficult part - if you break the power button circuit, you're ready for another new keyboard.

If it was not working well, then it's not such a big problem, you have nothing to loose or you can use an external power switch - hard to believe someone will go for that.

You will need a 55-60V power supply but you have to find a way to have the current limited at 10 mA! Again, 10 milliamps, in case the power button resistance decides to get lower, it will prevent the weak metal film trace to get melted instantly. Also you will be going to press on the button for couple of times, to make sure it goes from 60V to almost 0V and back.

You need to solder 2 wires:

Use the capacitors side for ground and solder a small wire on the pad with the red arrow. Be sure not to mistaken with another one. With wires soldered it's much easier to work and measure!

I used an adjustable power supply with readings on the voltages and amps! I could see the effectiveness of the pressed power button, the amps reading maxed out at 9 mA! I did not kept long on the button press, just briefly.

So after couple of cycles, I put back the keyboard and surprise, the voltage reading was now 3.4V on standby and the magsafe adapter light was again green on my A1181 MacBook.

It acted normal until now, hoping it will last, not sure what makes the button to drop in resistance, maybe metal particles trapped inside the click cup under the power button. I think it's a manufacturing flaw, normally this should not happen. It's sealed so there should be no humidity issue.

Happy fixing and post your results if you try this fix.