I purchased a IIfx that appeared to be in great shape. No battery leaks. Light capacitor leakage (no damaged traces). I recapped it and cleaned it with an ultrasonic cleaner.
With the original memory in Bank A and Bank B, I would get sad mac chimes. In Bank A only, it would chime but not activate the NuBus video card or continue to boot. I'd experienced this before when Bank A memory is bad (or loose) and nothing is in Bank B. I tried new memory sticks. No luck.
Looking more closely at the original RAM SIMMs, my heart sank. What is this crud? It turns out that leakage from C24 took an unusual path -- across the SIMM slots. Usually, C24 leaks down towards UI18.
As you might have guessed, this means the teeth on the SIMM slots are also covered in crusty corrosion. I did not want to endanger an otherwise working machine by desoldering and replacing the SIMM sockets.
I tested all kinds of chemicals on the corrosion on the original RAM SIMMs: isopropyl alcohol, vinegar, rust remover, deoxit, tarn-x, etc. While some of the corrosion responded, the black areas were unchanged. It didn't respond to a soldering iron with flux. A rubber eraser might have done a little bit, but also resulted in scratching the clean tinned areas.
The black chunks are solid but brittle. Sometimes picking at it will break off a small piece.
Then an idea came to me: why not use the same tool that dentists use on plaque and tartar? Amazon sells a plaque remover (dental scaler) tool for $25.
It is battery powered. It has a little metal tip that vibrates silently and imperceptively at 40 kHz. If you press it against your finger, nothing happens. If you press it against something solid but brittle, it makes a horrible screeching noise and the brittle object pops off or explodes in a puff of smoke. Think of it like a tiny fast hammer. Flexible material just bounces around. Malleable material like copper gets slightly worked. But, this hard corrosion cracks and crumbles.
Below is an image of the teeth in the RAM socket. The black areas are non-conductive and prevent the computer from functioning. I tried cleaning them with a pink rubber eraser, which only made things worse with pieces of eraser getting stuck in gaps. But, look at the one tooth that I used the plaque remover tool on! While not yet perfect, notice all the black dust that has come off. This took just a couple of seconds.
I cleaned all of the bad teeth with the plaque scaler under a microscope. I then cleaned away the dust with a compressed cleaning solution (MG Chemicals Super Wash). Then I wiped them all with isopropyl alcohol and a sponge cleaning swab. I repeated this process. During the second pass, I noticed I was getting a mirror finish on most of the teeth. Hurray!
And guess what? It worked! The IIfx is fully operational and passes Mac Test Pro RAM tests. (I used new memory -- not the crusty sticks shown earlier).
TIPS
The dental scaler really is a great tool to add to your arsonal.
1. The narrow tip is beneficial in that it let's you target very small areas without damaging anything else. The downside is that large areas require a lot of labor and patience.
2. The unit automatically shuts off after 10(?) minutes. Because it is quiet except when exploding debris, you might think you've cleaned that spot. A few seconds later you realize it is just shut off. No big deal.
3. I have not tried it with a chemical at the same time. Might be more effective?
4. The tip is stainless steel and it will scratch surfaces if you drag it. But, if you lift, move, and press down it doesn't scratch. Think of reverse-stippling.
5. It will expose pits and scratches and other damage. This is usually caused by the corrosion and you're just revealing it with the tool. I found the tool itself to be gentle except on the strongest mode and when you lean into the workpiece.
6. It works well on rust as well. I used it to remove the black material from a rusted SE/30 chasis after cleaning with Evapo-Rust. Most people don't mind the black coating. But, at least you have an option now.
MORE ABOUT THE IIFX
A couple of notes about the computer that was repaired.
Capacitor C1 exploded and caught on fire on the first power up. This is a well known flaw, as Apple installed 16V capacitors where they should have used 25V derating. Wife asks "What's going on in there?"
An unusual arrow sticker and possible resolder work on a couple of pins on the left-most NuBus slot. Given how difficult the board was to remove (the plastic clips had very crisp tips -- unworn), I suspect this was a factory repair.
- David
With the original memory in Bank A and Bank B, I would get sad mac chimes. In Bank A only, it would chime but not activate the NuBus video card or continue to boot. I'd experienced this before when Bank A memory is bad (or loose) and nothing is in Bank B. I tried new memory sticks. No luck.
Looking more closely at the original RAM SIMMs, my heart sank. What is this crud? It turns out that leakage from C24 took an unusual path -- across the SIMM slots. Usually, C24 leaks down towards UI18.
As you might have guessed, this means the teeth on the SIMM slots are also covered in crusty corrosion. I did not want to endanger an otherwise working machine by desoldering and replacing the SIMM sockets.
I tested all kinds of chemicals on the corrosion on the original RAM SIMMs: isopropyl alcohol, vinegar, rust remover, deoxit, tarn-x, etc. While some of the corrosion responded, the black areas were unchanged. It didn't respond to a soldering iron with flux. A rubber eraser might have done a little bit, but also resulted in scratching the clean tinned areas.
The black chunks are solid but brittle. Sometimes picking at it will break off a small piece.
Then an idea came to me: why not use the same tool that dentists use on plaque and tartar? Amazon sells a plaque remover (dental scaler) tool for $25.
It is battery powered. It has a little metal tip that vibrates silently and imperceptively at 40 kHz. If you press it against your finger, nothing happens. If you press it against something solid but brittle, it makes a horrible screeching noise and the brittle object pops off or explodes in a puff of smoke. Think of it like a tiny fast hammer. Flexible material just bounces around. Malleable material like copper gets slightly worked. But, this hard corrosion cracks and crumbles.
Below is an image of the teeth in the RAM socket. The black areas are non-conductive and prevent the computer from functioning. I tried cleaning them with a pink rubber eraser, which only made things worse with pieces of eraser getting stuck in gaps. But, look at the one tooth that I used the plaque remover tool on! While not yet perfect, notice all the black dust that has come off. This took just a couple of seconds.
I cleaned all of the bad teeth with the plaque scaler under a microscope. I then cleaned away the dust with a compressed cleaning solution (MG Chemicals Super Wash). Then I wiped them all with isopropyl alcohol and a sponge cleaning swab. I repeated this process. During the second pass, I noticed I was getting a mirror finish on most of the teeth. Hurray!
And guess what? It worked! The IIfx is fully operational and passes Mac Test Pro RAM tests. (I used new memory -- not the crusty sticks shown earlier).
TIPS
The dental scaler really is a great tool to add to your arsonal.
1. The narrow tip is beneficial in that it let's you target very small areas without damaging anything else. The downside is that large areas require a lot of labor and patience.
2. The unit automatically shuts off after 10(?) minutes. Because it is quiet except when exploding debris, you might think you've cleaned that spot. A few seconds later you realize it is just shut off. No big deal.
3. I have not tried it with a chemical at the same time. Might be more effective?
4. The tip is stainless steel and it will scratch surfaces if you drag it. But, if you lift, move, and press down it doesn't scratch. Think of reverse-stippling.
5. It will expose pits and scratches and other damage. This is usually caused by the corrosion and you're just revealing it with the tool. I found the tool itself to be gentle except on the strongest mode and when you lean into the workpiece.
6. It works well on rust as well. I used it to remove the black material from a rusted SE/30 chasis after cleaning with Evapo-Rust. Most people don't mind the black coating. But, at least you have an option now.
MORE ABOUT THE IIFX
A couple of notes about the computer that was repaired.
Capacitor C1 exploded and caught on fire on the first power up. This is a well known flaw, as Apple installed 16V capacitors where they should have used 25V derating. Wife asks "What's going on in there?"
An unusual arrow sticker and possible resolder work on a couple of pins on the left-most NuBus slot. Given how difficult the board was to remove (the plastic clips had very crisp tips -- unworn), I suspect this was a factory repair.
- David
