Amiga a500+ battery leakage repair

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Amiga a500+ battery leakage repair

Post by Steve » Fri Oct 08, 2021 2:50 pm

Just been working on @mrbombermillzy 's a500+. He had already neutralised the acid but required repair work on the eaten away traces. Special thanks to the absolutely amazing tool Amiga PCB Explorer without it this would be a nightmare. I really wish we had something like this for Atari!!!

Just a note on battery damage and how it can affect the physical properties of PCB's and solder. Firstly it can penetrate underneath the solder mask (the green protective layer) and eat away at the copper, it then spreads as far and wide as it can, through traces and vias (the holes that travel between PCB layers, front to back) When acid comes into contact with solder (on component legs or in vias) it seems to eat away the lead and just leave a crumbly crud which doesn't conduct electricity anymore. So it is really important to replace this crumbly crud with fresh solder, but - as it isn't proper solder anymore it can be super difficult to remove, it takes a lot of time and patience.

Coloured in purple are the affected areas that will need work
1. original shot beginning.jpg
1. original shot beginning.jpg (444.12 KiB) Viewed 141 times
You can see the acid has traveled all the way up to the chip legs, this means the traces and vias will be extremely weak and I will need to be extremely careful when removing the chip for cleaning the area
2. acid on chip legs.jpg
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Acid had travelled down to the ram expansion bus, so this will also require removing extremely carefully and cleaning
3. acid on expansion.jpg
3. acid on expansion.jpg (164.07 KiB) Viewed 141 times
As mentioned before, the solder on these resistor legs are crud and so they need lifting and the vias need cleaning. I also scraped away the corrosion on the copper layer underneath the old battery and put a layer of solder over it. Normally I'd use clear over-coat but I don't have any at the moment! The diodes and resistor in the audio section also needed patching together since the trace was gone.
4.  lift all resistor legs.jpg
4. lift all resistor legs.jpg (370.96 KiB) Viewed 141 times
Expansion header removed, ready for cleaning
5. expansion removed.jpg
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Chip removed, ready for cleaning
6. remove chip.jpg
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A nice bath in the ultrasonic for the expansion pins and chip
7. ultrasonic.jpg
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Chip socketed, as at this point I can't be 100% sure the chip works and therefore installing a socket is important
8. finish socket chip.jpg
8. finish socket chip.jpg (342.75 KiB) Viewed 141 times
As you can see, there is light shining through these vias now, where as before they were full of grey crud
9. light through vias.jpg
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All the broken traces are now patched up!
10. final.jpg
10. final.jpg (629.36 KiB) Viewed 141 times
All working, yay!
11. working.jpg
11. working.jpg (335.83 KiB) Viewed 141 times

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Re: Amiga a500+ battery leakage repair

Post by Badwolf » Fri Oct 08, 2021 3:10 pm

Well done, Steve!

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Re: Amiga a500+ battery leakage repair

Post by PhilC » Fri Oct 08, 2021 3:43 pm

Nice explanation of the repair @Steve , it's surprising how far away the acid can go if given a chance.
If it ain't broke, test it to Destruction.

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Re: Amiga a500+ battery leakage repair

Post by mrbombermillzy » Fri Oct 08, 2021 6:01 pm

Great job Steve! :D

2MB Chip RAM, I cant wait... :cheer:

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