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Purchasing computers with battery leaks.

G

generic486

Experienced Member
Joined
Mar 30, 2012
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290
Location
Australia
Since I got my Model 65sx going, I've been fasinated with the 386 achitecture. However, the Model 65sx brought consideraby restrictions upon me. The most annoying of theses restictions was that it only used MCA and thus the installation of other cards that I have (95%ISA) is not possible. So I happened upon a 386sx a few days ago and it is a very nice machine but one thing bothers me. The mobo battery has leaked. I have managed to dodge dead mobo and have been lucky that battery leaks so far have only been skin deep but this seller has clearly noted that this motherboard has leaked and has taken pictures.
386-corrosion.jpg

I got a little bit a shock when I saw that however, luckily, it all seems to be very recent so I hope the sooner I get it the sooner I can clean it up and hopefully have a working machine. Does anything look unrepairable as in are there parts on the mobo that are susceptable to damage and are unrepairable?
 
Actually, this looks pretty decent in the universe of battery-damaged motherboards. You can even assess the damage by leaving the motherboard in the machine and simply clip the battery out and scrub the area with a bit of water or water+alcohol mixture, dry and then see if it will power up. It's hard to tell from the photo, but I suspect that you'll even have a 3- or 4-pin header for attaching an external battery somewhere on the board--and I'd definitely go that way.
 
Nothing obviously fatal there. The board design has kept low trace density near the battery. Even if some of those traces have been corroded right through, they are patchable with fine wires on either side of the board. Possibly some of the capacitors legs are chewed through, at worst the keyboard socket might need replacement. I'd clean first with a dry brush, then use diluted white vinegar and toothbrush to remove the corrosion (rinse afterwards with water - vinegar is acidic), then check all the potentially damaged traces with continuity test.
 
Good to know, I see the external battery connector to the left of the battery. I always remove any battery from any vintage computer even if it hasn't leaked because it will eventually and the sooner the better. I always clean the mess with vinegar and then some distilled water. I have heard of some people using rubbing alcohol, is that okay too?
 
The electrolyte from this (apparently) NiCd battery is potassium hydroxide. It's soluble in water and alcohol (H20 solubility is 121g/100mL; similar in alcohol). The solubility of the reaction product between potassium hydroxide and vinegar is nearly twice as great (293g/100mL), but you still have to get both off the PCB. Around electronics, bases tend to be more tame than salts or acids, so I'd stick with water and alcohol and leave out the vinegar.

This is purely my opinion--the amount of potassium hydroxide leaked from your cell doesn't appear to be large in any case--and ultimately I think the method of cleaning doesn't matter, so long as you get everything cleaned up.
 
I'm of a totally different opinion. I have a large stack of 386 and 486 boards that have been hit by this battery plague. After lots of work and close attention they're all still dead. Anybody wanna buy'em? :)
 
Stone said:
I'm of a totally different opinion. I have a large stack of 386 and 486 boards that have been hit by this battery plague. After lots of work and close attention they're all still dead. Anybody wanna buy'em? :)
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I wonder how would these behave if you give them the "oven trick" that they try with modern video cards when they artifact. Placing it in the oven for just enough time for the soldering material to melt and then re-solidify. In this way, contacts that were previously broken might reconnect.
 
Stone said:
I'm of a totally different opinion. I have a large stack of 386 and 486 boards that have been hit by this battery plague. After lots of work and close attention they're all still dead. Anybody wanna buy'em? :)
Click to expand...
... and when you've sold all yours I've got a boxful or two...
 
When I see that kind of degree of battery leakage damage, I worry about the possibility that the 'green gunk' has travelled up the leg of a component and managed to work its way into the component (where if it hasn't already caused the component's failure, may do so down the track).
 
modem7 said:
When I see that kind of degree of battery leakage damage, I worry about the possibility that the 'green gunk' has travelled up the leg of a component and managed to work its way into the component (where if it hasn't already caused the component's failure, may do so down the track).
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Ditto. The fact that this has climbed the entire Keyboard connector and has made its way into an ISA slot has me worried. Still, if it were mine for free, I'd take a stab at cleaning it up. I wouldn't pay for the privilege, however, unless it came with some really juicy parts and accessories that I couldn't live without.
 
Hoo, not too good. At first glance, it doesn't look like it's spread too far. However, on second glance, it's spread several inches around the bad battery. If the prongs on the ISA slot are corroded, then the corrosion has probably spread lots farther than it looks like in the picture. It's definitely worked its way under components where a brush won't get.

Chop that battery out and scrub the heck out of it with alcohol first. Second, toss it in the dishwasher on a gentle setting. That sounds crazy, but as long as there's no juice going through the board, just let it dry completely and it's safe enough.
 
I've had some luck with a drop of distilled water, a pinch of baking soda, and tooth bush. Don't expect a miracle but it does clean up pretty good.
 
I have a 386 board that had corrosion in one of the ISA slots but it was only on the top surface (not the pins in the board), cleaned up find and the board works after I replaced the keyboard connector. Basically I just washed and scrubbed the whole board with warm water and dish soap with oxy. Some traces were etched a little but nothing was broken, seems stable with the testing I did. I had a 486 SLC board where traces were broken around the keyboard connector (and the keyboard plug was solid blue green crystals) which I cleaned and fixed with a few wires bypassing the damage on the bottom side of the board. Overall I would not bother unless the boards were important to me (the 486 SLC is rare and sold by a local company I liked) and the damage is minor (board posts but has issues). Since I have a ton of 386 and 486 motherboards working on a damaged one is not something I would have to do. You can still find a 386 or 486 MB for $15 or so or ebay if you look long enough.
 
I've talked to the guy and have decided on a BIN of $20. Even if it does not work there are still some really neat parts in it like 1.2MB 5.25 floppy, SIPP ram, 387 copro. IF it work then that will be great but if it doesn't maybe be a consultation or two may get it too work, i hope.
 
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