Power Mac G3 (Blue and White) PRAM battery explosion/corrosion

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Level 1

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Power Mac G3 (Blue and White) PRAM battery explosion/corrosion

Hello

I am back on these threads as I recently received a blue and white Power Macintosh G3 (350MHz, although not sure which revision yet). When I opened up the machine, immediately I saw that its PRAM battery had exploded, and likely had been that way for a while. (Pictures are below). Thankfully, it seems that most of the acid leaked down towards the bottom of the case, although there is a little bit of acid on the board right under where the battery sits. The battery holder leads are also quite corroded.

Now, on the listing for this machine, the previous owner did show it powered up and running, which may suggest that things are fine inside and that it does work, however I am a little hesitant right now on powering it up. I removed the exploded battery with a plastic pry bar thingy and started to put in a spare battery to test it, but I stopped as I would at least like to clean up the mess inside the case before doing so. So, #1, is it worth trying to at the very least clean the corroded battery holders? What risks are there in doing so based on the pictures below? #2, are there other things I should look out for as a result of this battery having blown up?

A few side notes that I should mention, the rest of the machine is quite clean. I didn't notice anything else on the board that looks broken or suspicious. The only other issue that made me sad was that some of the panels were cracked up, but that wouldn't affect it mechanically.

Thanks for any help!

Posted on Dec 28, 2019 7:55 AM

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Answer 1

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Wind5387 Author

Level 1

8 points

Dec 28, 2019 1:32 PM in response to Jan Hedlund

Thanks Jan and Allan for the info. I have a quick update with pictures.

I was able to take it apart enough to see the other side of the board. I don't see any other corrosion or battery acid at all on that side, nor do I even see any signs of battery acid on the space directly below the board (i.e on the metal door nor plastic panel on the door). It seems that the battery may have exploded "away" from the board, however, as I mentioned above most of the corrosion is on the bottom of the case. I also saw a clear, kind of oily liquid under the hard drive plates, both of which showed corrosion/rusting on the bottom. In the pictures below, you can see that it pooled up under the main HD tray. I also noticed it seems to have splattered further over on the non-door side of the case, and some of it is actually on the plastic panel. AND I noticed some of the packaging in the box this thing was in appeared to have soaked up some of the liquid. I wiped up some of the liquid that was under the HDD bays up with a paper towel.

Other than the bit of acid that is lodged in the battery holder, the board is dry and I didn't observe any corrosion at all on that corner of the board itself, nor on the case.

So this is my update, and as always thank for any further assistance!

~ Wind5387

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Answer 2

Jan Hedlund

Level 7

22,513 points

Dec 28, 2019 10:01 AM in response to Wind5387

Yes, you could try to clean the battery holder (but judging by the photographs, it will not be easy). However, the circuit board under the battery holder (and the other side of the board) may also be damaged, so it would probably not be a bad idea to remove the entire board for inspection. Based on that, you could then decide what to do next (further cleaning and/or repair of broken traces, et cetera). For more information about problems related to bad batteries and capacitors, you may want to visit a site specialised in older Macintosh computers (for example, 68kmla.org).

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Answer 3

Jeff

Level 6

12,088 points

Dec 31, 2019 10:55 AM in response to Wind5387

Duracell batteries typically have their label affixed so that the DURACELL name and other info are printed from left-to-right, when the battery is on its side and the positive end (battery top) is on the left. In your photo showing the corroded battery in its holder, the battery appears to be installed with its polarity reversed. What I assume to be the battery's positive terminal is oriented toward the motherboard's (-) "MINUS" marking. This would explain the battery leaking. Those lithium batteries can be dead for years, without leaking any solution on the motherboard. I've found that the household product "C-L-R" (Calcium-Lime-Rust) Remover (usually for kitchen and bathroom problems) is very effective in removing corrosion from battery slot terminals, if they aren't heavily damaged. I apply some to a Q-tip and dab at the corrosion. You may find that the metal has been damaged to the point of breaking through, so that after removal of the corrosion, it falls apart. If that happens, you may have to remove and replace the battery holder — if you're concerned about repeatedly unplugging the computer from A/C power and losing the PRAM settings. Some people run the computer without a battery in place. The 3.6-volt, ½AA lithium battery is also available with "axial leads" - a wire lead at each end of the battery for soldered applications, such as this Saft battery. If you're skilled with a soldering pencil, you could remove the damaged socket and install that type, unless you can find a replacement socket on ebay. Double-check that the polarity is correct before soldering in place.

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Answer 4

Wind5387 Author

Level 1

8 points

Jan 1, 2020 4:15 PM in response to Jeff

Interesting you mention that. I wish I took more pictures and paid more attention to its orientation in the holder, however based on those pictures above (and a couple more), I actually think it was mounted correctly in the thing, but at this point I can't really say. However, after giving the inside of the machine a nice clean, putting in a spare battery, and also performing a few resets on the board, I got the thing to fire right up, and it seems to work very well!

I did try starting it without the battery in, which only worked one time, as all other attempts afterwards there was no picture upon bootup.

Now all of this just gave me another problem, which at this point, I know will not be an easy nor cheap fix at all, and has to do with the 17-inch CRT Apple Studio Display that came with the machine. Long story short, I think the flyback transformer just burned out. When pressed the button to turn that thing on for the first time, there was a very alarming static sound, followed by crackling/popping and some flashes from the screen. It put out picture just fine on the first boot after fixing the Power Mac, but later that day it started doing this. Now, the only thing it does is make two different "click" noises when I press the power button, and that's it. The still button turns green though, and it still makes that weird electrical feedback noise when I plug it in (the sound of it being "warmed up").

Thanks!

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Answer 5

Allan Jones

Level 9

69,362 points

Dec 28, 2019 10:24 AM in response to Wind5387

The underside of the circuit board may be affected as well. That could cause fatal damage to the conductive traces underneath.

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Power Mac G3 (Blue and White) PRAM battery explosion/corrosion

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