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Extracting Denise and Paula reveals some corrosion on the pins.

Fat Agnus appears to have been spared, but I don't have a proper PLCC extractor tool and I'm not going to risk prying it out with kludgy methods.

Against best advice, I took the risk to power up the board in its present state.

The power LED flashing 6 times means that the Kickstart's diag routines failed somewhere, and a red screen signals a ROM checksum failure:
https://www.amigalove.com/viewtopic.php?t=324

This is actually great news: the 68030 was able to execute some ROM code and even write into some of Denise's registers.

The checksum error could also be caused by a fault on either the data bus or the address bus.

Today I received the first batch of components for my A3000 board. Just a few DIP sockets, common logic IC, diods and capacitors.

I couldn't find 48-pin DIP sockets for Denise and Paula, so instead I bought 24-pin sockets to be used in pairs.

I scrubbed most of the green goo with a combination of sand paper and fiberglass pen.

I frequently cleared the dust from the PCB with an ESD-safe brush, distilled water and isopropyl alcohol.

I should probably also wash the entire board with soap water, but I'm not sure which soap is safe for PCBs, and which components need protection.

And this is what was underneath all the corroded metal oxide.

Most of the copper directly under the battery has been completely corroded, exposing a dark fiberglass layer.

This was actually lucky: that big ground plane neutralized most of the leak, reducing the damage on the rest of the PCB.

It's time to clear the corroded components, starting from the RTC circuitry south of the battery.

I used a $30 electric vacuum pump iron on the back of the board to suck most of the solder from the pins.

Then I pulled gently from the front while heating the area with a heat gun.

Most solder would melt easily, but pins attached to GND or heavily corroded would need more heat.

@codewiz I had problems in these places. Even further away, where you wouldn't have expected it.

Every dark pattern is a suspect. And it hides well under the components.

If I get a battery damage to my desk - usually I do not even bother to power it on. But good to see your amiga half to life in this state allready!

...and if you invest in lab equipment: A microscope has changed a lot for me

@trebroNdotnet Two traces on the bottom left are indeed open, but they're just the raw audio L/R signals going to the video slot. I won't bother reconstructing them for now.

The ICs above the battery belong to the Amber subsystem, which works for me. I don't believe they're causing the vertical lines every 16 pixels. Those must be a short of some kind on the Denise data bus.

The Denise socket has some corrosion and should be replaced, but I'm waiting to get a better desoldering gun for that.