Sorry this may be a little OT for the forum. But you guys are great with hardware so I'd thought I would ask.

I'm repairing a classic Macintosh SE/30. When I pulled the logic board out, I noticed it has green "fuzz" all over the place. The caps have more than likely leaked. Common problem with machines that old.

Anyway, the board also has a "1/2 AA" battery. I admit, I've never seen one labeled "1/2 AA". I would have thought it would be labeled "A". But sure enough, it's about half the length of a AA battery.

Fortunately, it hasn't leaked. It's rated at 3.6V but it's only producing about 1.0V. I wouldn't keep it anyway.

The logic board has to have it. And since it's a classic Macintosh, it's not the easiest machine to open up. Also, it's very tight on space in there.

To replace, I'm pondering two scenarios. One, try and find the "1/2 A" battery and hope it doesn't leak. Two, find a more common "watch type" battery and maybe solder in some wires for it. I might then be able to enclose the smaller battery inside a plastic box that would, hopefully, contain any future leaks.

What are your suggestions?

Thanks!

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Cat; the other white meat.

Beware that the green fuzz may eat copper and other conductors - anywhere you had to clean, and anywhere nearby, might be physically delicate or no longer making a connection.

Looks like there are several names for this battery size, and they are easy to get from the usual suppliers:
½AA
SAFT LS14250
Tadiran TL5101
UL142502P
CR14250 - note only 3V
ER14250

I would suspect any battery that's 3V or more would be good enough, but of course it's safest to replace like with like.

Ideally, store a machine with batteries removed, or check them annually and be ready to replace them if flat.

That's true. I plan on giving the board a good soak/scrub this weekend. I've read that some people have even put them in hot water with soap. Just need to let it dry for 7-10 days.




Ah, thanks for that!




So true. It's becoming harder for me because I have 70+ vintage computers. Only the 16 bit machines have batteries and I'm pretty good about taking them out of those machines. But all of them have caps. So I have to constantly inspect my boards to see if anything is leaking. It's a full time job.

lol

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Cat; the other white meat.

Batteries are indeed an interest for some of our projects. I'm no chemist, but can safely say from experience that if the leaking battery is alkaline (high pH), then white vinegar (acidic, low pH) is the stuff to use to clean up the mess; and if the battery uses acid (like carbon-zinc, zinc chloride, or lead-acid, and probably other types too), then a baking soda solution is what you use to clean it up. I've recently cleaned up alkaline-battery messes with a Q-Tip and white vinegar, and I couldn't believe how quickly and easily and thoroughly it cleaned up. Really nice. Then just use water to get all the vinegar off. No need to soak for a long time. I think soap's pH is usually pretty high, and it may leave an unwanted film which may conduct a little current.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Great info. However, the battery hasn't leaked. It's just dead. I want to replace it with a better battery. I'm just wondering if it's worth the effort to get a different type of battery that is less likely to leak. I know *any* of them could leak....

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Cat; the other white meat.

You could consider using long leads, then mounting the replacemet battery somewhere where leakage isn't an issue.

More off-topic: I'd seriously like to know how it is that NiCad batteries, which cause green fuzz that destroys copper, also cause blue fuzz that destroys gold in exactly the same manner.

No one I've asked this of has been able to answer it. I wonder if anyone here knows.

I am not a chemist, but I can speculate that the "fuzz" in both cases is the by-product of reaction between the metal and the attacking chemical. Gold is much harder to corrode than copper, but it can still be done with a bit of effort and/or bad luck.

Mike B.

I'm not a chemist either, but somehow the battery juice alters the electronegativity of the metal and the fuzz is oxide of the metal, the way I understand it. Maybe I'm wrong, I don't know. The best example of this that I know of is what aluminium does when it comes in contact with mercury.

Again I could be wrong, but the process with blue fuzz on gold traces from a NiCad doesn't appear to take significantly more time/effort than the green fuzz with copper. I base this solely on the amount of damage I've seen. From things manufactured in the mid 1980s, I actually see more instances of damaged gold than copper, for whatever reason. Perhaps though, gold traces are thinner, or only gold -plated, I don't know. That would change things.

Buy 10 HP calculators that came with replaceable NiCad batteries, from eBay, and nine of them will have severe cases of blue fuzz on and replacing gold PCB traces. At least, that's been my experience.

Might be worth noting that gold plating in electronics is not just gold:
"In general, a 0.8 micron (30 micro inches) coating of hard gold over a minimum of 1.3 microns (50 micro inches) of nickel"

Edit: and hard gold is not pure gold - may contain Cobalt or Nickel.

and I suspect the gold is porous and the blue fuzz is not a gold compound but a nickel one. I do have a friend with a Ph.D. in chemistry, but he's kind of hard to get hold of.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

OK, it makes much more sense if nickel is the culprit. Gold does not oxidise at all, as far as I know, and even if it did, I don't think it's possible to make anything combined with gold to be blue. I'll have to read up on nickel.

The "A" size cell is, apparently, larger, just as the AA cell is larger than the AAA cell. Fortunately, while not exactly common, 1/2 AA cells are fairly easy to source, either via eBay, or Amazon, or your local Radio Shack if you still have one.


Note that older macs used a 3v battery, and they had problems keeping the RTC and PRAM running long-term, which is why Apple switched to the 3.6v setup in the first place.

From https://en.wikipedia.org/wiki/Battery_(vacuum_tube): Here's a "A" battery, for filaments of tubes in "portable" (definitely not pocket-sized) equipment:



The "B" battery was a high-voltage one for the tubes' plate voltage. They weren't all the same voltage. I've seen 45V ones, and Wikipedia says they were made in 120V, 90V, 67V, and 45V:

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

But the C battery was not what we call a C battery.

Watch out for that B++ battery!