Today was bathing time!
From left to right. Distilled water with a dash of Simple Green, Acetic acid mixed with distilled water and finally pure water. There is also a forth bowl with IPA not shown in the picture. I usually start by scrubbing off any ooze, corrosion and minerals that are on the board. When I have a bare copper surface, that is only tarnished from oxidation, I put it in the vinegar bath until the copper is shiny again (a few minutes). Then I wash it in pure water to remove the acid. You may add sodium bicarbonate, but watch out if you use baking soda. Sometimes manufacturers add other stuff to the sodium bicarbonate as well. Check the package first. Then drown it in IPA. Depending on the time it was in the water I usually leave it in there for a while to remove all the moisture. Finally I use compressed air to blow off the IPA. If there are still some stains, reapply IPA, and then immediately wash with distilled water, then soak in IPA again. Usually these are flux residues that get dissolved in the IPA, but rinsing with water while the IPA is still liquid usually takes care of the stuff.
Once I am done with cleaning and the copper looks good again, I apply a layer of solder to protect the copper for all eternity
This is the A15 Board as an example:
I removed the capacitors and the diode in the middle, which looks like this:
after some scrubbing, the green copper sulfite (from a leaking tantalum capacitor probably replaced by the previous owner) the corrosion is gone, but we are left with a layer of oxide. I is impossible to solder to this oxide layer, so we need to remove it first.
Unfortunately I did not take a photo after the acid bath, but only after I was completely done.
I overdid the solder patch a little in this case. This pad was a GND pad, but the plated holes had no contact, because the copper was already gone around those. So I just poured it with solder then washed it again, leaving a shiny blob of solder
The three tantalum caps looked new (old stock?) to me and their capacitance and ESR (a little more than 1 Ω @ 100 Hz) seemed fine so I left them in for the moment, but I will replace them as soon as Mouser ships my replacement caps (long, long time...)
I also paid that corroded polystere capacitor a visit with the fibreglass brush. Worked like a treat:
Then retinned the lead:
So far so good. I cleaned most of the boards shown in the previous post and I also cleared out the interior of the case so see how far the battery acid had spread:
I think I will try the vinegar again and then some polish to touch it up. We will see how it goes. While life was looking good a new horror crept up on me; the A3 Multiplier Assembly:
I can hear a rattling inside and there is stuff rolling around
I did not yet open it, because the screws have been massively abused and I was running out of time anyway. I guess this could be the board where the previous repair attempt met a gruesome end.
To be continued...