Amiga 500+ Restoration Attempt

[TheM]

Last month I finally managed to acquire Rock Lobster of my own!

Unfortunately, battery has leaked badly:
http://1drv.ms/1Dntm0N



This stuff found it's way even on some of the rear connectors -- no idea how it got there.

I removed the battery, gave it a good scrub with diluted vinegar and then started removing affected parts.
So far got the expansion connector off (replacement arrived yesterday).
Custom chips look fine, all chips with crap on them are standard 74 parts so ordered a bunch of those and sockets from eBay and AliExpress.
That's the easy bit.

However, on some parts of the motherboard it looks like it leaked under the clear coat. Most look unimportant (empty or just test points) but there are some areas where there are larger traces (around edges of the expansion cut out). The traces haven't been eaten through yet, but they will be if left like that.

I've never tried to restore motherboard affected with battery rot before. Anyone here done it before and can share some lessons learned?

Cheers,
Harvey

[TheM]

Just can't get rid of the green rot:
http://1drv.ms/1Fcqdzi

[Carcenomy]

Dude that rot looks pretty well advanced

Not sure what you can do from here to clean up after that.

[TheM]

I decided that chances of finding a gentle way to remove that are not very high and if not removed A500+ is a write off. The only thing left to try was some careful dremeling.

The result:
http://1drv.ms/1En2ZEp

And finally:
http://1drv.ms/1H9LL3g

It didn't work. A500+ won't start. The best I got was it displaying once all error colours except red (so green, blue and yellow) but even that only once.

[tezza]

Hmm. Oh well, it was worth ago. Sometimes that acid damage is just too sever.

There seem to be a lot of A500s on Trade Me in various conditions. Maybe try to snag a cheap replacement?

[TheM]

> There seem to be a lot of A500s on Trade Me in various conditions. Maybe try to snag a cheap replacement?

Standard A500s are plentiful, but A500+ are rare.

I have four working common A500. I considered just transplanting a late revision of A500 board into A500+ case, replacing custom chips with those from A500+ and soldering extra RAM but that wasn't my first choice.

[Voyager1701e]

Sorry to drag up an old thread....just curious....did you make any further progress on this one? Would be a shame to lose a +, as you say they are the rarer of the species

Did you check to continuity (top and bottom) around where the board was damaged? Did you remove and replace the custom chips (as many Amiga repairs are as simple as removing and replacing the chips in sockets)?

[TheM]

I made no further progress, unfortunately.

I spoke with a guy who used to be Cbm technician in Auckland and he suggested the same -- most of their repairs consisted of replacing custom chips until it started working. I tried removing the chips and discovered that none have unobstructed access from both sides so without a chip extractor tool I'm more than likely to bend or snap pins if I try with a screwdriver or similar. I have a small DIP chip extractor but for this I need a rather large one plus PLCC extractor for Agnus. I planned to buy some but never did.

Another thing that disheartened me is that if the problem really is with a busted custom chip(s?) I have nothing to replace it with. I should have at least one spare set of OCS chips but have no spare ECS and populating 500+ board with OCS chips seems pointless.

I can't remember if I ever did the continuity test, though... I was going to do it but I think I forgot. I'll have to check that; I did replace several smaller chips and could very well be that I damaged a trace somewhere.