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Attempting to repair a Classic with a horrendous Maxell battery explosion (aka Mission Impossible)


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I acquired a Classic about a week ago for a good price, but I didn't know the condition of it, I was just hoping it would be an easy recap job...

I opened up the case to be greeted by a half rusted chassis and a Maxell battery explosion on the logic board.

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So I quickly set to work trying to undo the mess created by the battery acid.

The chassis is half destroyed, the side closest to the battery has suffered badly, it even has holes in it.

 

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The first challenge was to remove the logic board from the chassis, but this proved difficult because of all the corrosion on the chassis rail that the logic board slots into. With some elbow grease/force, I managed to separate the logic board from the chassis.

 

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At this point, with the logic board removed, it was now easier to see the extent of the chassis damage.

 

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I started to inspect the condition of the logic board...

 

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Put simply, the logic board is a disaster, with many damaged traces visible straight away. I attempted to remove the battery from its holder, but the whole thing (battery + holder) just fell off immediately, obviously nothing was holding it onto the board anymore.

 

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Good bye battery...it was nice knowing you.

 

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The first job is to try to clean as much of the corrosion/crud off as possible, to get back to a clean board/bare copper. At first sight this looks completely ruined, like there is no going back, but let's see what I can do......

 

So plenty of isoproyl alcohol and lots of swabbing later... and we're looking like this:

 

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I lost D1 and Y1 in the process of cleaning, a diode and crystal that form part of the clock circuit.

 

At this point I also removed C1 and C2.

 

Moving on... I kept cleaning and scraping, adding some baking soda to help clean further.

 

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At this point I could tell there was something not right about UA2 (the real time clock chip) - so I removed it...and it took some traces with it (excuse the flux mess):

 

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So after cleaning again, and also removal of C3 and C4 and cleaning up the pads:

 

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I haven't really looked at the back of the board up to this point, there is some damage there too. This concerns me as I wonder if there is irreversible damage between layers of the board?

 

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I also cleaned some other parts, including the front bezel and the fan shroud/fan, and I made a start on sanding the chassis.

 

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Some of the chassis rust is really quite bad, so I'm not sure if this will be saved or not, but I will keep at it for now...

 

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And that's all I have for now.

 

Am I mad? Is this stupid? What is the point? These are all questions I'm asking myself, but I keep coming back to the fact I have nothing but time to lose, and this is a really good chance for me to improve my trace repair skills.

Hope you enjoyed reading. :b&w:

 

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On 1/9/2021 at 3:07 PM, joshc said:

These are all questions I'm asking myself, but I keep coming back to the fact I have nothing but time to lose, and this is a really good chance for me to improve my trace repair skills.

 

There's nothing wrong with working on a far gone Mac if it allows you to hone your skills. Rather make a mistake and learn from it on a totalled board than on an actual board repair!

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I'm restoring a Mac XL / Lisa that had a lot of corrosion damage on the frame parts. I removed the rust with Muriatic acid. It worked great, but that stuff is super nasty. I was taking them to a plating shop who does bead-blasting and chemical rust removal anyway, so it was super not worth it. You should be able to take your frame to a local plating shop and they can sort it for you. The finished part will still have pits though. I recommend getting it zinc or nickel plated. They should be about the same price.

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With that kind of rust, there's nothing he can do.

 

most good metal is already gone, i have a frame similar to the one in the picture, big portions fell apart a couple of years ago and small units are still falling today.

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  • 3 weeks later...

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