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Macintosh Classic FAN direction

Kab

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I am replacing the fan in a Macintosh Classic. The fan is on the bottom of the machine. When I pulled the old fan, I found it was set to pull air INto the machine, rather than blow it out. With the fan being on the bottom of the machine, that makes sense. But when I found a drawing of the Classic with all parts in blow-up, the fan looked to be oriented witht he exhaust blowing out. To me, it makes more sense to have the fan’s exhausted blowing IN since this fan is on the bottom of the machine. The air would be hitting the logic board. So, …is this correct?
 

GiGaBiTe

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There is no correct orientation for the fan, no matter if it pushes or pulls, it will be ineffective all the same. The fan is a bolted on kludge to fix Job's idiot design philosophy. The logic board isn't what you have to worry about, it's the analog/power board where all of the heat is generated.

Steve Jobs demanded that the original 1984 Macintosh have no vents, holes or fans of any kind "because MY PRECIOUS". The final design had tiny slits for convection, but that was grossly inadequate. As a result, predictably the machine hideously overheated from having a smoking hot vacuum tube in a hot box. High failure rates and warranty repairs galore ensued. Jobs never learns from his mistake, this wasn't the first time, nor the last that he would create a hot box oven that baked itself to death. The Apple /// from 1980 had even worse problems with heat because it had literally zero vents. The 1998 iMac G3 was another with just convection cooling, it also gets smoking hot.

It wasn't until the Mac SE in 1987 did the compact Mac eventually get a fan. It and the SE/30 were the *best* cooled out of the lot, and they still had overheating issues on the analog board and power supply.

The Classic has the fan in a weird location because of the combo analog board + power supply, CRT and memory expansion board prevent the fan from being installed on the rear.
 

Kab

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There is no correct orientation for the fan, no matter if it pushes or pulls, it will be ineffective all the same. The fan is a bolted on kludge to fix Job's idiot design philosophy. The logic board isn't what you have to worry about, it's the analog/power board where all of the heat is generated.

Steve Jobs demanded that the original 1984 Macintosh have no vents, holes or fans of any kind "because MY PRECIOUS". The final design had tiny slits for convection, but that was grossly inadequate. As a result, predictably the machine hideously overheated from having a smoking hot vacuum tube in a hot box. High failure rates and warranty repairs galore ensued. Jobs never learns from his mistake, this wasn't the first time, nor the last that he would create a hot box oven that baked itself to death. The Apple /// from 1980 had even worse problems with heat because it had literally zero vents. The 1998 iMac G3 was another with just convection cooling, it also gets smoking hot.

It wasn't until the Mac SE in 1987 did the compact Mac eventually get a fan. It and the SE/30 were the *best* cooled out of the lot, and they still had overheating issues on the analog board and power supply.

The Classic has the fan in a weird location because of the combo analog board + power supply, CRT and memory expansion board prevent the fan from being installed on the rear.
Ok. So: Do you know which way Apple engineers wanted the fan set?
 

Chuck(G)

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When the Macintosh first came out, I recall that Steve Jobs proclaimed not only would it be made right here in America, but it would not have a fan to make noise.
My opinion on the latter was that it was a bad decision.
 
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Timo W.

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When I pulled the old fan, I found it was set to pull air INto the machine, rather than blow it out.
Which is correct. Even to this day, a fan on the front/bottom pulls air in (since air there is cold), and a fan at the back/top blows it out (since warm air soars up). Don't mess with that - unless you want the system to overheat.

Steve Jobs demanded that the original 1984 Macintosh have no vents, holes or fans of any kind "because MY PRECIOUS". The final design had tiny slits for convection, but that was grossly inadequate. As a result, predictably the machine hideously overheated from having a smoking hot vacuum tube in a hot box.
No idea what this has to do with the Mac Classic. The Classic has a fan and needs it anyway because of the hard disk inside.

The original 1984 Mac was a machine no one ever built before. A "first try" is never perfect from the beginning. Also, since when do CRTs run "smoking hot"?
 
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GiGaBiTe

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Which is correct. Even to this day, a fan on the front/bottom pulls air in (since air there is cold), and a fan at the back/top blows it out (since warm air soars up). Don't mess with that - unless you want the system to overheat.

The Macintosh Classic has a single fan, the one he's talking about. It does not have a rear fan. I found a good exploded view of the machine:

3-Desmontaje-Macintosh-Classic.jpg



No idea what this has to do with the Mac Classic. The Classic has a fan and needs it anyway because of the hard disk inside.

The Hard Drive is the least heat producing device in the machine, the analog + power board is where all of the heat is produced, and the CRT. Like I already said, the orientation of the fan doesn't matter that much, because of the tiny highly restrictive vent holes. It will be recirculating more hot air than anything due to its poor placement inside the machine.

Also, since when do CRTs run "smoking hot"?

When they're crammed in tiny boxes with lots of hot electronics and virtually no ventilation. They get smoking hot. CRTs normally run very hot, why do you think basically every monitor has a large grille above the CRT? Compact Macs just have ity bity tiny slats inside the handle. The hole in the back doesn't really serve much purpose when the hot air gets trapped at the top of the case.

If the OP wants to properly cool the machine, I'd recommend attaching an external fan to the back grille pulling air out of the machine. If you want to get creative, you can use a smaller fan and put a small baffle inside the case to have a push/pull setup. Where half the grille has air going in and the other half has air going out. It will be more effective than the internal fan and reduce heat stress on the machine significantly.
 

AndyO

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Looking at the grille on the fan screen in my Classic, the dust is all on the outside, so yes, it pulls air in. And actually it is quite effective, even if only from the temperatures next to the analog board when the fan runs, versus when it doesn't (accidental experiment when I forgot to reconnect it).

The other stuff... yeah well, if I had to put my money on who knows best about the hardware, I'd go with Apple's engineers. Nobody is perfect, but those folk had more than just opinions to work with.
 

GiGaBiTe

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The other stuff... yeah well, if I had to put my money on who knows best about the hardware, I'd go with Apple's engineers. Nobody is perfect, but those folk had more than just opinions to work with.

Apple engineers back then did amazing things working with extremely limited resources, and carefully sneaking around Jobs, who was a walking disaster wherever he went.

folklore.org has a lot of info about what went on in the early days of Apple and the trials and tribulations they went through building the original Macintosh.
 

AndyO

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Apple engineers back then did amazing things working with extremely limited resources, and carefully sneaking around Jobs, who was a walking disaster wherever he went.

folklore.org has a lot of info about what went on in the early days of Apple and the trials and tribulations they went through building the original Macintosh.
The Classic (being the system the thread is about) wasn't the original Macintosh, and Steve Jobs left Apple in 1985, well before the Classic was designed. For sure he was a divisive character, and had some 'difficult' views and opinions, but as compromised as the original Mac was by his views, the Macintosh went on to become one of the most influential platforms in computing history.

The point being, the Classic was not a Jobs product, and (I would contend) the engineers who produced it were not stupid. The fan (which was the question) is what they intended it to be, working the way they wanted it to work. Jobs wasn't there to influence that for good or ill, and personally, I am quite astonished by the fact so many of these machines, built to a strict price constraint imposed by John Sculley, are still in working condition, or recoverable with relatively simple fixes such as cleaning/recapping.

I'm well aware of folklore.org, and it actually adds a lot of color and nuance to what is often told as a pure pro/anti Jobs history - well worth reading. Otherwise, I'm not sure what Jobs was, or wasn't, is much to do with the question. A different one, perhaps.
 
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