A Tale of Two Systems (And their Horrible Batteries) Part 1

In parallel, I’ve started fixing both the Amiga 2000 and the Quadra 950 boards. Both had extensive battery damage. In both cases I’d neutralised the battery alkaline with vinegar, water and isopropanol washes.

I started with the Amiga.

AMIGA 2000

Evaluating the board, I ended up pulling off all components and sockets in about a 10cm radius circle around the battery. This included the 68000 CPU, the resistor packs and lots of capacitors in the area. After that I was able to check what was damaged. Amazingly there only seems to be two bad traces and one bad via at this point. I patched the traces with kynar wire on the underside and used a thin leg from a resistor to replace the via.

Denuded. the patched via is visible next to the “BAT3” notation.

I’ve ordered replacement resistor packs, as well as replacements for all the capacitors that were nearby. Most seemed corroded, so I’m not taking chances. I also ordered some replacements for the generic 74 series logic that had been nearby.

I replaced the keyboard connector and the joystick port with parts sourced locally. I also replaced the battery with a non rechargeable CR2032 coin cell holder, with some slight changes to the circuit in the area. I was able to find the diode I needed at Artifactory, which saved me a trip.

I finished off the harness for the power supply. I “stole” an ATX off an old PC motherboard that had died. I simply wired through all the appropriate pins. I’m waiting on a 7905 voltage regulator so I can make a -5V rail for the system.

The white wire is the -5V. The brown wire is the no longer needed “tick” wire.

I also located and changed the “tick” jumper on the main board so the system is no longer looking for a tick signal from the PSU. Amusingly I found it in an old Usenet post where the first person replying was David Haynie, the engineer for the later Amigas and the second post was Dr Peter Kittel, one of the leads of the Amiga support team from Germany. Straight from the horses mouth as they say.

I’ve also ordered parts so I can build a keyboard adapter, similar to the one I made for the Archimedes, just for the Amiga 2000 instead.

I also fitted the original on/off switch to drive the ATX connector instead of the mains.

Use the video slot cover.

At this point I’ve got as far as I can reasonably get without more parts. They should be in early next week.

Many parts back on the Amiga, plus the 950 before I started removing SIMM sockets.

MACINTOSH QUADRA 950

This one has been tough going. It’s got 16 SIMM sockets in joined pairs and 8 of them have battery damage. Serious damage too.

The corrosion has, in many cases, turned all the solder into some strange salt. no amount of heat will turn it back to solder, and new solder won’t stick to it until it’s removed. Thankfully it’s not impacted the copper on the traces as badly, and in most cases mechanical removal works as the salt just crumbles out of the through holes.

The first pair. I literally pulled out most of the pins with tweezers. There was no real solder left to hold them in once the plastic surround had gone.

This did, however mean I had to mechanically break up the SIMM sockets completely. I used a pair of side cutters and cut through the SIMMS bit by bit, removed the plastic and then concentrated on the pins. This usually consisted of snapping off the tops and pulling through the remains of the pin with tweezers, or in some cases, a really hot soldering iron.

Only the SIMMs in the direct line of the acid spill needed this much effort, however. The other rows joined to these ones were simply removed with the desoldering station and very little fuss. At worst I needed to add just a bit more solder a couple of times and maybe scrape back some oxide off the solder to expose fresh metal below.

6 of 8 done. Only 1 pair to go.

I still, as of writing this article, have one pair of SIMMs to remove, but as these have taken the least hit, I’m not too worried about them.

So far I’ve found one bad trace and damaged two more while working on this, so I’ll need to bodge them back in before I seal everything up.

Amazingly you can still buy 30 pin SIMM sockets new! I’ll need 8 so nearly $50 worth. I just hope I can get all this working at the end of the day 🙂

Published by ilike8bits

I collect old computers and consoles

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