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Macintosh Classic battery disaster

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Recently I got a macintosh classic that have the checkerboard screen issue. When I opened the machine, I saw a huge corrosion mark under the analog board.

I thought it would be some leaking capacitors like many macintosh of this model have, I was ready to recap boards.

But it's not. Actually no capacitors have leaked, it's the PRAM battery that opened up completely (litteraly).

The analog board seems to be fine but the mainboard has been corroded so much that the battery holder has desoldered. I've tried to clean up some of the corrosion with isopropyl alcohol but there's still a lot of this brown heap.

I'm now looking for help on how bring that board back to normal running; like get rid of the corrosion and maybe rewire some pcb tracks and put an PRAM equivalent battery.

The machine powers up fine to the checkerboard screen, I tested it before opened it.


Here's pictures of the disaster:



The leak corroded the chassis.


1490554274-dscf0136.jpgWhere the leak occured, the battery holder was where the corrosion heap is. It affected some of chips legs and resistors on the other side.



The dead battery. The top is  slightly open.


1490554919-dscf0143.jpgThe battery and its holder. The holder is completly ruined and was desoldered by the corrosion.


Hoping that you can get me some help


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Maxell strikes yet again!  Damnit Jim!


The battery acid will have leaked under the ICs and the main processor.  It eats the traces and vias.  Realistically, I don't think you can save this board.  You can try scrubbing it with a toothbrush and some white vinegar for a while, or even put it in the dishwasher.  After it's clean, you're going to have to get a meter and ohm out every single trace and via and run rework wires to complete any broken ones.  The ICs with a lot of green growth on them, it can corrode into the component itself, so those may have to be replaced as well.  From experience, when you try to remove them, the acid will have dissolved the pads underneath, or loosened them so they come up with the component.


So sad to see stuff like this..

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At least you can try to salvage the chassis! But I think the logic board is too far gone to be brought back to life unfortunately.


Get some white vinegar, disassemble the Mac completely (remove the front bezel, fan etc... to isolate the chassis) and dump the chassis in a large bucket with the vinegar for about 1 hour. Then try to scrape off the rust with an old toothbrush. It should come off easily. 

One of my SEs also fell victim to the dreaded Maxell battery. Managed to save the chassis that way. Currently trying to save the logic board (mine isn't as bad as yours)


Good luck!

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Whats funny is I hear all of these Maxell horror stories, yet I have a couple of completely intact Maxell batteries. Sorry about that, but everyone else is right, your logic board is done xx(.

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I have only been successful in resurrecting a dead battery damaged board once. So the chances arnt great. 


It could be fixed if you have limitless time available, so personally its beyond "economical" repair. 

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