Yet another vintage computer falls victim to an on-board NiCd battery... As bad as it looks, it is actually repairable, but repairing the damage takes a considerable amount of time.
Dave, I know you stay very busy, but could you stabilize the Lisa's boards so they won't corrode further, so that you or someone else could have a better chance at repairing them in the future? I briefly mentioned the technique in the
Acorn Archimedes A3000 thread. The links I provided to the classiccmp email archives don't currently work, but
this link to archive.org does. Someone found a Gridcase with a board that looked
like this and used this technique to clean it up.
Basically, you clean the entire affected area (multiple boards in the case of this Lisa) with white vinegar and scrub at it lightly with a toothbrush (even get down into the card edge sockets, although they will likely need to be replaced later). The NiCd material that leaks from the batteries is highly alkaline, so the vinegar, being a mild acid, will neutralize it. You then need to rinse the boards with lots of water in a sink to make sure you flush out all the vinegar because any remaining vinegar would also be mildly corrosive. Flushing with vinegar and scrubbing away any buildup will stabilize the boards and stop further corrosion. Simply cleaning with isopropyl won't neutralize the battery mess and even if you clean off a lot of it, without neutralizing, the boards will corrode up again.
The next step, if you wanted to go a little further with cleaning, would be to lightly scrub the corroded areas using a baking soda and water paste with a toothbrush, followed by another water rinse. This will remove the bulk of the surface corrosion on any exposed copper traces, component leads, etc. and also helps neutralize any remaining vinegar.
The cleaning/stabilization technique is very simple, but a little messy, so you'll want to clean the boards in a sink. Some people claim you need deionized water for this sort of thing, but I've been using tap water to do this for decades and have yet to have any issues with it.
As for the discoloration and tarnish under the solder mask, once the board is neutralized with white vinegar, it shouldn't corrode further. Unless there is already a break in a trace, those discolored spots are best left alone.
This company sells replacement card edge connector fingers and the tools necessary to install them. Maybe they would be willing to send Dave a full kit and/or take on these Lisa boards as an extreme repair example? The examples I've seen of their in-house work have been excellent, but it is an expensive service. These type of repairs are almost always going to be reserved for boards which are simply not replaceable.
The phrase "Not economical to repair" doesn't really come into play for stuff like this Lisa. This is basically a restoration project for a serious collector, and not something an electronic repair tech could justify repairing at an hourly rate. Unlike a repair tech, a collector can spend as much time on it as he would like.
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