exxos's Atari, Amiga & retro forum

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

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

Acid had travelled down to the ram expansion bus, so this will also require removing extremely carefully and cleaning

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.

Expansion header removed, ready for cleaning

Chip removed, ready for cleaning

A nice bath in the ultrasonic for the expansion pins and chip

Chip socketed, as at this point I can't be 100% sure the chip works and therefore installing a socket is important

As you can see, there is light shining through these vias now, where as before they were full of grey crud

All the broken traces are now patched up!

All working, yay!

Well done, Steve!

BW

Nice explanation of the repair @Steve , it's surprising how far away the acid can go if given a chance.

Great job Steve!

2MB Chip RAM, I cant wait...

And here we have the returned motherboard fitted back into its immaculate A500+ case...


Now to (very quickly) test it. Ive managed to grab a floppy set of the game Road Rash. (Please excuse the mess in the background!)


Looking good Steve, thanks.

Of course, I have yet to perform thorough testing and the ultimate test is being used with a CPU accelerator drawing more current through those copper veins, but that's for another day, spare time being at an all time low ATM.

However, it looks like Steve has done a great job here, and he doesn't muck about time-wise either!

Awesome thx @mrbombermillzy

Nice work!

What should I use to clean motherboard from Battery acid?

And what to use in supersoonic bath?

The NiMH battery juice is actually an alkali and not an acid. To neutralise the chemical you can use white vinegar and then clean with water.

Nice work, I like to spend spare time repairing 500+ boards and getting them back in service, it's quite rewarding.

For future reference:
Those logic chips can be tested in a TL88 eprom programmer, the bundled software has a test.
It's a cleaner look to run the patch wires on the underside. Tops side is of course functionally fine though

Oh and well done on removing that header for the expansion port without messing it up. Those can fall to bits easily.

PaulJ_2.0 wrote: ↑Fri Oct 22, 2021 9:21 am Nice work, I like to spend spare time repairing 500+ boards and getting them back in service, it's quite rewarding.

For future reference:
Those logic chips can be tested in a TL88 eprom programmer, the bundled software has a test.
It's a cleaner look to run the patch wires on the underside. Tops side is of course functionally fine though

Oh and well done on removing that header for the expansion port without messing it up. Those can fall to bits easily.

Cheers Paul. Yeah I ran fresh solder through the entire expansion port first to 'loosen up' the cruddie grey solder, then used my desoldering gun & then a little blow of the heat gun to just loosen it out without pulling traces.