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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.

Except for the Ricoh RTC, the components I pulled are cheap to replace and can be cut in place to minimize damage to the precious #Amiga 3000 board.

I went to Microcenter and bought full assortments of resistors and capacitors, each for $9.99:

https://www.microcenter.com/product/618896/inland-1-4-watt-1-resistors-610-pack

https://www.microcenter.com/product/632685/inland-047uf-1000uf-electrolytic-capacitors-assortment-kit-13-values-200-pcs

I had already ordered some DIP sockets and ICs at Mouser, but I forgot the common 14-pin sockets, which are on their way.

Luckily, I have with me a debug tool from the future: the Z3660 is an open hardware accelerator which can optionally emulate a full 68040 CPU with UAE's open-source JIT running on a modern ARM core:
https://github.com/shanshe/Z3660

I bought this baby at AmiWest for my A4000, but now it will come handy to probe the A3000 PCB from a working system.

The Z3660 can load Kickstart files from an SD-card and map them to the ROM region, allowing me to use the awesome DiagROM to test RAM, I/O ports, audio and more:
https://www.diagrom.com/

Those vertical bars flash on and off. They're probably caused by a faulty data line between Denise and Fat Agnus, or perhaps between Fat Agnus and the Chip memory bank.

The Chip RAM banks pass all memory tests, so we can exclude them.

The Z3660 can also boot off an emulated SCSI controller, loading hard-disk images from the SD card.

The OS image that came preloaded with my board throws a recoverable guru while booting, but then boots to Workbench.

There are a couple of hardware diagnostic tools, including SysInfo and WhichAmiga.

Overall, the system is really unstable, hanging every few minutes. Tapping on Denise is a reliable way to trigger a crash.

Also, rebooting with Ctrl+Amiga+Amiga results in a permanent black screen. I inspected the reset logic, and /CPURST remains low forever.

I can't tell whether there's a problem with the A3000, but other Z3600 owners confirmed it shouldn't happen.

Debugging all these quirks would be much easier with an oscilloscope. I should take this project to a shop with proper lab equipment...

Tonight I'm going to the Artisans Asylum, a huge #hackerspace and workshop co-op in Boston:
https://www.artisansasylum.com/

Their electronics shop has all the tools I need for my #Amiga 3000 restoration project and several experts who can advise.

The #Amiga 3000 fast RAM uses the infamous Zig-zag In-line Package (ZIP).

The pins were very easy to bend when installing the chips. Indeed, I found one with a bent pin! Was it like that from the factory? ...or did someone already try to fix this several years ago?

Anyway, re-seating all the ZIP chips didn't improve stability, so I ended up removing all of them.

The Z3660 uses the Z-Turn can map 128MB of its own RAM to the Amiga address space.

Using modern hardware to sidestep hardware issues on the A3000 board feels a bit like cheating, but ZIP RAM modules are rare, expensive, and... a stupid idea even back in 1990!

#commodore
#amiga
#vintagecomputing
#retrocomputing
#electronics

With on-board Fast RAM disabled, the system is stable enough to run Lotus Turbo Challenge... up to a certain point!

This crash is 100% reproducible. I don't know whether it's caused by a hardware problem with the ECS chipset or this game is simply incompatible with the 68040.