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lprovenI have managed to repair my Mac Classic II, which makes me happy. After a few incidents of Simasimac when powering it on, overcome by trying a few times, it died altogether a month ago.
But I did it in a strange and unfamiliar and rather scary way. I took out its logic board, removed its SIMMs & carefully pried its 4 DIL ROM chips out of their sockets...
And ran it through a cycle in my dishwasher.
After that, I carefully scrubbed the worst-damaged areas of its logic board with an old toothbruh and lots of hot water, dried it thoroughly overnight in the airing cupboard, reinserted it...
And it worked! My compact Mac bonged happily and booted successfully first time!
Good news for me, bad news for![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
technofairy, who wanted to make it into a Maquarium.
But why did this work?
Simasimac is generally caused by failing electrolytic capacitors.
Capacitors ("caps") are one of the 1st bits of electronics to fail in older computers. By electronics, I mean non-moving-parts; machinery with motors dies first, usually. Fans, then disk drives.
Caps work like tiny batteries with a very short charge/discharge cycle, "smoothing out" the flow of current by absorbing bursts and releasing it in a slow & measured fashion, like a dam on a river.
This means they effectively charge & discharge millions of times.
Cheaper caps are generally of the "electrolytic" type. They work via a chemical reaction occurring within them each time, like batteries. And like batteries, they eventually fail.
When they fail, like old batteries, their contents react in an uncontrolled fashion. Often the volume of reagents increases, bursting the seams of the cap and allowing electrolyte to leak out. Thus, the computer suffers problems from some of its components not working correctly any more, causing partial failures - things like sound becoming fainter and fainter. However, it's worse than that. This electrolyte is by nature reactive, so now the computer has dribbles of conductive liquid running across its circuit boards. If these reach an IC (an Integrated Circuit - a "chip"), the liquid might run across the chip's legs, making a short circuit ("short") between them. It might make short circuits over longer distances between components, too, but caps are small things, so there's not a lot of liquid, meaning that this is less likely.
Short circuits cause major problems and are quite likely to make a computer stop working altogether.
What's worse, the electroytes are often corrosive and with actually corrode any metal they contact, causing it to go white and fuzzy instead of smooth and shiny. This reduces the efficiency of contacts between components and the fuzz itself can be slightly conductive and thus cause shorts.
So, failing caps leak, and thus cause 2 stages of problem: first, intermittent or transient or partial failures, like dimming screens, sound output getting quieter or perhaps occasional crashes. Secondarily, leaking electrolyte causes short circuits within the computer, causing problems like "simasimac" and then total failure.
But electronics are tough. They're made of metal and ceramic and plastic. As long as they're not working at the time, they're waterproof. If they are working, water is conductive, so causes massive shorts. If the shorts occur between power circuits and logic, the large electrical currents flowing through delicate little circuits can blow them altogether, causing permanent damage. Even bringing a computer in from storage in a cold place into a warm room can cause condensation to form within it, leading to this damage, which is why you mustn't turn on a computer that's been subjected to this for a few days - time to allow the condensation to dry.
So if you can remove the part affected by cap leakage, isolate it from any parts that might sustain water or heat damage, like electric motors or displays or fans or power supplies, then it's safe to wash it, so long as you dry it thoroughly before you try to use it again.
So, you remove your dead logic board and run it through the dishwasher.
Why a dishwasher? Well, it's non-mechanical cleaning. There are no brushes or anything in contact with the board and it's not moving or being shaken or agitated as it would in a clothes washing machine. So delicate components, such as those on legs, shouldn't be damaged, as they might by simply scrubbing it under a tap. All that happens is that the board gets repeatedly sprayed with hot soapy water in a hot wet environment for an hour or so, time to loosen and dissolve dried-on deposits of electrolyte and other nastiness. If it gets off all the electrolyte, and the cap isn't leaking any more or has dried up, the computer might start working again. If the cap is now only working marginally or wasn't completely essential in the first place, dishwashing can effect a cure.
It won't remove corroded metal, though, so in severe cases, it won't help. But if the machine's already dead, there's nothing to lose.
It's also a lot easier than trying to remove and replace the failed cap, especially if you are not familiar with component-level electronics work, particularly soldering. Added to this, more modern computers from the 1990s often used robots to do the soldering, allowing tricky techniques for humans such as surface-mount attachment instead of the older pin-through-hole attachment. Sadly this was also a time when computer prices really started to drop hard, forcing manufacturers to work hard to economize - e.g. by using cheaper capacitors, which die after 10 years or less. This problem happens to PCs, too, especially the overclocker's favourite, the Abit BP6 motherboard, which with very modest hacking let you build a dual-450MHz PC out of two £50 300MHz Celeron processors.
(Also, Apple in particular got a habit of crippling their low-end machines so as not to steal market share from their more lucrative high-end kit. That's why my poor little Classic II has its RAM limited to only 10MB and cripples its 32-bit 68030 processor by running it on a 16-bit bus, making the Classic II dog-slow compared to the SE/30 it replaced, which ran the same CPU - and had an expansion slot and over 10× the RAM expansion. If anyone knows of an SE/30 going spare anywhere, I would love one!)
Anyway, surface-mount components are really difficult for even a skilled solderer to replace, and when you consider that the parts may be hard to obtain and the contacts on the board corroded, it's an uphill battle.
By the way, dishwashers are also good for keyboards that have been killed by spilling drinks into them, although this works best for 'boards with indivudual microswitches under them, not ones that use a rubber or plastic membrane. Just soak those in the bath for a while, in warm soapy water, rinse thoroughly, dry for several days in a warm dry place - lots of tiny nooks and crannies to hold water in a keyboard - and try again.
But I did it in a strange and unfamiliar and rather scary way. I took out its logic board, removed its SIMMs & carefully pried its 4 DIL ROM chips out of their sockets...
And ran it through a cycle in my dishwasher.
After that, I carefully scrubbed the worst-damaged areas of its logic board with an old toothbruh and lots of hot water, dried it thoroughly overnight in the airing cupboard, reinserted it...
And it worked! My compact Mac bonged happily and booted successfully first time!
Good news for me, bad news for
technofairy, who wanted to make it into a Maquarium.But why did this work?
Simasimac is generally caused by failing electrolytic capacitors.
Capacitors ("caps") are one of the 1st bits of electronics to fail in older computers. By electronics, I mean non-moving-parts; machinery with motors dies first, usually. Fans, then disk drives.
Caps work like tiny batteries with a very short charge/discharge cycle, "smoothing out" the flow of current by absorbing bursts and releasing it in a slow & measured fashion, like a dam on a river.
This means they effectively charge & discharge millions of times.
Cheaper caps are generally of the "electrolytic" type. They work via a chemical reaction occurring within them each time, like batteries. And like batteries, they eventually fail.
When they fail, like old batteries, their contents react in an uncontrolled fashion. Often the volume of reagents increases, bursting the seams of the cap and allowing electrolyte to leak out. Thus, the computer suffers problems from some of its components not working correctly any more, causing partial failures - things like sound becoming fainter and fainter. However, it's worse than that. This electrolyte is by nature reactive, so now the computer has dribbles of conductive liquid running across its circuit boards. If these reach an IC (an Integrated Circuit - a "chip"), the liquid might run across the chip's legs, making a short circuit ("short") between them. It might make short circuits over longer distances between components, too, but caps are small things, so there's not a lot of liquid, meaning that this is less likely.
Short circuits cause major problems and are quite likely to make a computer stop working altogether.
What's worse, the electroytes are often corrosive and with actually corrode any metal they contact, causing it to go white and fuzzy instead of smooth and shiny. This reduces the efficiency of contacts between components and the fuzz itself can be slightly conductive and thus cause shorts.
So, failing caps leak, and thus cause 2 stages of problem: first, intermittent or transient or partial failures, like dimming screens, sound output getting quieter or perhaps occasional crashes. Secondarily, leaking electrolyte causes short circuits within the computer, causing problems like "simasimac" and then total failure.
But electronics are tough. They're made of metal and ceramic and plastic. As long as they're not working at the time, they're waterproof. If they are working, water is conductive, so causes massive shorts. If the shorts occur between power circuits and logic, the large electrical currents flowing through delicate little circuits can blow them altogether, causing permanent damage. Even bringing a computer in from storage in a cold place into a warm room can cause condensation to form within it, leading to this damage, which is why you mustn't turn on a computer that's been subjected to this for a few days - time to allow the condensation to dry.
So if you can remove the part affected by cap leakage, isolate it from any parts that might sustain water or heat damage, like electric motors or displays or fans or power supplies, then it's safe to wash it, so long as you dry it thoroughly before you try to use it again.
So, you remove your dead logic board and run it through the dishwasher.
Why a dishwasher? Well, it's non-mechanical cleaning. There are no brushes or anything in contact with the board and it's not moving or being shaken or agitated as it would in a clothes washing machine. So delicate components, such as those on legs, shouldn't be damaged, as they might by simply scrubbing it under a tap. All that happens is that the board gets repeatedly sprayed with hot soapy water in a hot wet environment for an hour or so, time to loosen and dissolve dried-on deposits of electrolyte and other nastiness. If it gets off all the electrolyte, and the cap isn't leaking any more or has dried up, the computer might start working again. If the cap is now only working marginally or wasn't completely essential in the first place, dishwashing can effect a cure.
It won't remove corroded metal, though, so in severe cases, it won't help. But if the machine's already dead, there's nothing to lose.
It's also a lot easier than trying to remove and replace the failed cap, especially if you are not familiar with component-level electronics work, particularly soldering. Added to this, more modern computers from the 1990s often used robots to do the soldering, allowing tricky techniques for humans such as surface-mount attachment instead of the older pin-through-hole attachment. Sadly this was also a time when computer prices really started to drop hard, forcing manufacturers to work hard to economize - e.g. by using cheaper capacitors, which die after 10 years or less. This problem happens to PCs, too, especially the overclocker's favourite, the Abit BP6 motherboard, which with very modest hacking let you build a dual-450MHz PC out of two £50 300MHz Celeron processors.
(Also, Apple in particular got a habit of crippling their low-end machines so as not to steal market share from their more lucrative high-end kit. That's why my poor little Classic II has its RAM limited to only 10MB and cripples its 32-bit 68030 processor by running it on a 16-bit bus, making the Classic II dog-slow compared to the SE/30 it replaced, which ran the same CPU - and had an expansion slot and over 10× the RAM expansion. If anyone knows of an SE/30 going spare anywhere, I would love one!)
Anyway, surface-mount components are really difficult for even a skilled solderer to replace, and when you consider that the parts may be hard to obtain and the contacts on the board corroded, it's an uphill battle.
By the way, dishwashers are also good for keyboards that have been killed by spilling drinks into them, although this works best for 'boards with indivudual microswitches under them, not ones that use a rubber or plastic membrane. Just soak those in the bath for a while, in warm soapy water, rinse thoroughly, dry for several days in a warm dry place - lots of tiny nooks and crannies to hold water in a keyboard - and try again.
