Macbook hardware troubleshooting help

[GlumReaper]

Hi guys,

I wonder if someone can offer me some advice? I bought I macbook off ebay with a known fault. The seller reported it shuts down after 20-30 minutes of use, and the fan grinds loudly sometimes. It sounded like a pretty easy cleanup and maybe replacement fan.

I've been playing with it for a few days now. The fault was as described (though the seller failed to mention that the screen had some discouloured patches of what looks like liquid damage and two of the keys including return don't work!) So I thought I'd open it up and have a look. I've never worked on an apple laptop before, but have repaired many windows laptops. I was following the illustrated disassembly guide from powerbookmedic.

Anyway, this macbook was filthy inside. Really really grubby, with sticky patches where it's obviously had a drink in it, and mainly full of dog hair! The heatsink and fan were clogged with it so it's no wonder it had overheating problems. I pulled it all apart and cleaned it up. I spent hours with cleaning cloth and a toothbrush. I replenished the dried-up thermal grease on the heatsink. I've put it all backtogether...

...and nothing. I seem somehow to have killed it! I followed anti-static proportions as normal (wrist strap etc) and was very careful. I'm sure I got everything back in the right place, but now I get absolutely nothing.

When I hit power, nothing at all, no sound, no light and nothing on the screen. The battery is showing fully charged, and when I plug in the magsafe power cord the light goes green after a second.

I've just re-seated the RAM and HD, which didn't help, and just followed through the top case removal procedure again and reseated the keyboard/touchpad connector - still nothing.

I'm a bit stumped now. Since I'm new to mac, I really don't know where to go next. What diagnostic steps would be best to take now?

Thanks a lot for reading!

 

[GlumReaper]

I carried on playing with this laptop after I posted. Something strange happened a little later on.

I'd removed the top case/keyboard to check connections, and had the laptop partly-disassembled on the table. I wanted to try and start it up again so I plugged the keyboard back in, attached the magsafe power cord (since the battery had been removed) and pressed power.

Nothing happened again so I left it to go and continue researching. I didn't unplug the power cable though. I came back a few minutes later and could smell a 'hot', almost burning smell. When I put my hand near the exposed innards of the laptop, it was really hot! It seemed to be mainly the CPU/heatsink, though on picking it up the back of the laptop was really hot too.

Can it have been somehow running? There was literally no activity - no HD, no fan, nothing on the screen. But could it have been trying nontheless to run? If not how else could it get so hot?

Please help me out with some advice!

 

[blackburn]

Where you careful with static? If you live in a dry climate you may have static build up on your body, and you may shocked the machine.. Else check for badly seated cables or anything that may be short-circuiting..

edit: ups you wrote that you where careful with static.. Maybe something shorting try do inspect the connectors..

 

[fluffyx]

You state you followed electrostatic discharge (ESD) precautions... did this include a grounding mat for the computer? If you wore a grounded wrist strap without grounding the computer, this would not have prevented ESD.

Also, cleaning with a toothbrush is 100% not advised. Unless you use an ESD-safe brush, the movement of bristles produces large static charges. Even if you, the computer, and your workstation were properly grounded, cleaning with a toothbrush easily could have damaged the board.

If the chips were getting hot and the fan was not running, the main logic board is definitely damaged.

•

We don't work on PCs, but it seems that because PC logic boards are larger, have fewer components, have wider traces, and the components are more spread out, they're less sensitive to ESD. Proper tools and work environment is important for any computer, but especially important for Macs.

 

[GlumReaper]

Thanks for the replies guys!

I did not have a grounding mat. I was using a glass tabletop though, which I normally assume to be sufficiently unable to conduct ESD.

I should've clarified, I only used the toothbrush for the plastic casing. For the boards and components I used a soft brush designed for computer cleaning (so I guessed it would be ok) and compressed air.

I've since read a bit more about the macbook, I'm going to try and disassemble and reassemble with extreme care and double-check all of the connections.

Thanks again.

 

[fluffyx]

Try connecting only the DC-in board (Magsafe board / power inlet) and the fan to the main logic board. You could even remove the main logic board from the enclosure if you wanted. When you ask the computer to power on, either by shorting the power button contacts or by connecting the top case and pressing the power button, the fan should spin. If the fan does not spin, it's safe to say the logic board is damaged and requires repair.

•

Glass does not conduct electricity, which means that glass tables are not suitable for ESD-sensitive components.

An ESD mat is dispersive—it slowly conducts charges away from items on its surface and into ground. A glass table top is insulative—it allows the items on its surface to build up a charge, and that charge is not removed. When you, who were grounded, touched your MacBook, which was insulated from ground, the charge differential between you (at ground) and the item (which is not at ground) produces a damaging spark. If the item were on an ESD mat and you were wearing a wrist strap, it would already be at ground, as would you, and no damage would occur.

A wrist strap is useless without a grounding mat, and vice versa.

A brush for cleaning computers is generally not ESD-safe. A brush for cleaning printed circuit boards will be labeled "ESD-safe," is not sold in most retail stores, and will be significantly pricier than a normal brush.

 

[GlumReaper]

By way of an update for anyone finding this thread later: It's all fixed now.

The macbook is working fine (though the fan is still rather noisy, I will replace it at some point).

I did another very careful disassemble and reassemble. What I found that I think must've caused the lack of POST, was a bent metal bracket under the logic board itself. This small bracket comes from under the black plastic liner and sits atop one of the screw posts that support the board. It must be for grounding. I found that this had been bent by my first re-insertion of the logic board such that it was either just not grounding or possibly even shorting the back of the board.

I put the clip back into place and then put everything back together. The mac has been working perfectly since.

Thanks for the replies!