carlo@osprey.cvs.rochester.edu (Carlo Tiana) (08/21/90)
I wonder if there is anything one can do to improve the cooling and reduce the dust intake in a Mac (a IIci specifically). I have had my IIci for about 9 months now. About 3 months ago, I opened the box for some reason and found it clogged with dust: over the electronics, over the HD (a 210 Mb Maxtor - which gets hot, normal heat, but probably needs a fan blowing air over it) and just about everywhere else too. I looked around a bit and noticed that the fan draws in cold air from just about any hole in the case and sends out hot air through the fan vents at the back. Cince the largest hole in the case is the floppy drive hole at the front, I wondered what the floppy heads felt about this, since they probably have accumulated as much dust as everything else (maybe this has some relevance to the floppy read/write failures people complain about every once in a while??). So I decided to turn the fan around, so as to have control over where the air came in from, and took a furnace filter (local hardware store, $0.95 or so), cut it to size to cover the (now localized) fan intake and (with some sweat, tape and incatations) mounted it on the back of my Mac. Sure enough, the filter is now all clogged up, but no big deal, I can cut another piece and replace it. But: should I do this? My Mac sits in a somewhat enclosed space (say 3'x3'x3') so the air does not circulate in an optimal fashion ;) and gets rather hot (there is a nice stream of hot air coming OUT of the floppy slot now!). In addition, the air from the fan now blows over the hot power supply, and, thus heated, over the HD.... Is what I am doing a big no-no? Are there any other solutions to avoid the interior of the machine filling up with dust? I may want to have enough space left in there for a NuBus board one day! I am sure the dust does not do anything any good. Also, I am sure my Mac was a lot noisier after 6 mo than it was when new, and I can only attribute this to dust (maybe lodging itself in the fan assembly?) Anyone else tried to fix this? Anyone else worried about this? Carlo. carlo@cvs.rochester.edu
starta@tosh.UUCP (John Starta) (08/22/90)
carlo@osprey.cvs.rochester.edu (Carlo Tiana) writes: > I wonder if there is anything one can do to improve the cooling and reduce > the dust intake in a Mac (a IIci specifically). I'm not sure what can be done to improve the cooling as my IIci has always been cool to the touch, but after reading your message I took a quick look (flash light to the front and rear) and sure enough, I can see plenty of dust forming in the vents and in the rear where it is exhausted. > I have had my IIci for about 9 months now. Eight months come the twenty-third. (I know, you were dying to know that right? I mention it merely for comparison purposes.) > Since the largest hole in the case is the floppy drive hole at the front, > I wondered what the floppy heads felt about this, since they probably have > accumulated as much dust as everything else (maybe this has some relevance > to the floppy read/write failures people complain about every once in a > while??). Actually, the largest overall holes in the case are the vents to the left of the floppy drive and those on the top and buttom of the case. You are right however, the floppy has sucked in its equal share of dust. With my brief flash light inspection, I could see dust on several outer pieces. The internals may be protected if there is no air escape, but I can't be certain of that. You might have something there with your theory, maybe an engineer or two from Apple can comment on it further for us. Please! > So I decided to turn the fan around, so as to have control over where > [...] > Is what I am doing a big no-no? Yes. Return the fan to its original position at once. It was designed to cool the machine. In the configuration you have it in, it is currently heating it. > Also, I am sure my Mac was a lot noisier after 6 mo than it was when new, > and I can only attribute this to dust (maybe lodging itself in the fan > assembly?) Come to think of it, I have noticed that too. I attribute some of it to recent hard drive troubles, but the rest can likely be attributed to the dust shrinking the size of the vent holes and beginning a low "whistle." > Anyone else tried to fix this? Anyone else worried about this? Not yet, but with the brain power of this net, I'm sure a logical solution will come about soon. I am worried, yes. My first step will be to give the machine a thorough cleaning this week. John
carlo@eagle.cvs.rochester.edu (Carlo Tiana) (08/24/90)
(I tried to mail this, but my system does not seem to like .uucp addresses) In article <6910N3w162w@tosh.UUCP> you write: >> So I decided to turn the fan around, so as to have control over where >> [...] >> Is what I am doing a big no-no? > >Yes. Return the fan to its original position at once. It was designed to >cool the machine. In the configuration you have it in, it is currently >heating it. Now why would that be the case? My machine is considerably hotter inside than the room outside. Any air circulation should improve things, should it not? Still, now you got me worried! I would like to figure out what to do though. My feeling with electronics is that if it works when you turn it on, the only thing you can do to break it is to overheat it; and the only way to do that is to put lagging (ie dust) over it! Carlo. -- carlo@cvs.rochester.edu -- carlo@cvs.rochester.edu
clarson@ux.acs.umn.edu (Chaz Larson) (08/24/90)
In article <9053@ur-cc.UUCP> carlo@eagle.cvs.rochester.edu (Carlo Tiana) writes: >In article <6910N3w162w@tosh.UUCP> you write: >>> So I decided to turn the fan around, so as to have control over where >>> [...] >>> Is what I am doing a big no-no? >> >>Yes. Return the fan to its original position at once. It was designed to >>cool the machine. In the configuration you have it in, it is currently >>heating it. > >Now why would that be the case? Seems obvious to me. In the standard configuration, the fan draws outside air into the front of the computer, pulls it through the interior of the machine, and exhausts the hot air out the back. When the fan is reversed, it draws outside air in through the back, blows it across the hot power supply [which heats it] and then into the interior of the machine, very likely increasing the internal temperature. chaz -- -- Opticians Discover Nancy Reagan Was Married to Abraham Lincoln in Previous Life. -spew clarson@ux.acs.umn.edu AOL:Crowbone
straka@cbnewsc.att.com (richard.j.straka) (08/24/90)
In article <6910N3w162w@tosh.UUCP> starta@tosh.UUCP (John Starta) writes: >carlo@osprey.cvs.rochester.edu (Carlo Tiana) writes: || I wonder if there is anything one can do to improve the cooling and reduce || the dust intake in a Mac (a IIci specifically). || Since the largest hole in the case is the floppy drive hole at the front, || I wondered what the floppy heads felt about this, since they probably have || accumulated as much dust as everything else (maybe this has some relevance || to the floppy read/write failures people complain about every once in a || while??). I would assume that the floppy drive does not generate any significant amount of heat. Some, of course, but probably not a LOT. For instance, the Plus' floppy survived OK without fan-forced cooling. Soooooooooo: Why not enclose the floppy in an airtight container (probably best left to Apple to design it right into the original product, but you don't have that option), and that way, no dust gets sucked in through the floppy. Doesn't fix the problem of general dust, but that's more easily dealt with. -- Richard Straka AT&T Bell Laboratories, IH-6K311 ------------------------------------------------------------------------ UUCP: att!ihlpf!straka MSDOS: All the wonderfully arcane ARPA: straka@ihlpf.att.com syntax of UNIX(R), but without the power.
miller@rsmas.miami.edu (08/25/90)
In article <2125@ux.acs.umn.edu>, clarson@ux.acs.umn.edu (Chaz Larson) writes: > In article <9053@ur-cc.UUCP> carlo@eagle.cvs.rochester.edu (Carlo Tiana) writes: >>In article <6910N3w162w@tosh.UUCP> you write: >>>> So I decided to turn the fan around, so as to have control over where >>>> [...] >>>> Is what I am doing a big no-no? >>> >>>Yes. Return the fan to its original position at once. It was designed to >>>cool the machine. In the configuration you have it in, it is currently >>>heating it. This simply cannot be the case unless the outside air is hotter than the inside air. >> >>Now why would that be the case? Why indeed. Read on. > > Seems obvious to me. In the standard configuration, the fan draws outside air > into the front of the computer, pulls it through the interior of the machine, > and exhausts the hot air out the back. > > When the fan is reversed, it draws outside air in through the back, blows it > across the hot power supply [which heats it] and then into the interior of the > machine, very likely increasing the internal temperature. > > chaz Ok, Chaz. Let's consider a little thermodynamics here. The fan, in its normal orientation, sucks a certain amount of air out of the box in a given period of time. If you reverse the fan, it still moves the same amount of air in that same amount of time only the air moves in the opposite direction. In other words, since the volume of the box does not change, we get the same volume of air exchanged with the outside regardless of which way the air moves. During that time, the Mac generates a certain total amount of heat. That heat is transfered from the Mac's components to the flowing air and is removed from the box either thru the fan or thru the vents depending on the orientation of the fan. Either way, the same total amount of heat is removed from the box. Now, if the fan is sucking air out of the box, a component residing near vent will be cooler than a component residing near the fan. If the fan blows air into the box, the opposite will be true. Thus, individual components may be hotter or cooler depending on which way the wind blows even though the total amount of heat removed from the box is the same. How much hotter or cooler? Putting one hand near a vent and the other near my fan I would guess the difference is less than 10 or 15 degrees. So, unless some component is already operating right at its heat tolerance, I suspect that there is no effective difference in the cooling capability of an inward versus an outward blowing fan. HOWEVER, if one puts a filter over the fan resulting in decreased airflow, all bets are off. I suggest that a filter combined with stronger fan blowing into the box might be a better solution to the combined heat & dust problem. ------------------------------------------------------------------------------- Jerry L. Miller INTERNET: miller@rsmas.miami.edu Rosenstiel School of Marine and Atmospheric Science, University of Miami Remember: "It's later now than it's ever been; however, vg'f zber yvxr vg vf abj guna vg unf rire orra orsber."
clarson@ux.acs.umn.edu (Chaz Larson) (08/25/90)
In article <8999.26d534ec@rsmas.miami.edu> miller@rsmas.miami.edu writes: >[ in response to my theory of why a reversed fan would heat a Mac IIcx >instead of cooling it, a fine explanation of the actual physics of the >matter] OK, here's what I was thinking. The internal layout of the IIc- is: <pardon the lame ascii graphics> fan vv __________________ | | | | | |____| | | | | | | | <power supply | |______| | | | | | | | | |________________| Now, I had assumed that the power supply would be one of the hottest components inside the case. Normally, the air is drawn through the case, where it "absorbs" some of the heat produced by the motherboard, etc., then is drawn across the power supply just before it is exhausted. If the fan is reversed, it blows air across the power supply, where [I had figured] it would pick up a lot of heat, which would reduce the air's ability to "absorb" motherboard, etc. heat, resulting in an increasing internal tenperature. All that said, however, I currently have my IIci open as I type this, and I find by poking around that the power supply is one of the coolest things in this box. various other parts, including the hard drive and some silver-jacketed boxes on the motherboard, are much warmer. So, I'm insane. Pardon my interruption and never mind. chaz -- -- Joan Rivers Slaughters Ninety-Five Chinese Physicists in drunken rampage. -spew clarson@ux.acs.umn.edu AOL:Crowbone
fswrr@acad3.fai.alaska.edu (rector walter r) (08/26/90)
In article <1990Aug24.131637.21844@cbnewsc.att.com>, straka@cbnewsc.att.com (richard.j.straka) writes... >In article <6910N3w162w@tosh.UUCP> starta@tosh.UUCP (John Starta) writes: >>carlo@osprey.cvs.rochester.edu (Carlo Tiana) writes: >|| I wonder if there is anything one can do to improve the cooling and reduce >|| the dust intake in a Mac (a IIci specifically). > >|| Since the largest hole in the case is the floppy drive hole at the front, > >Why not enclose the floppy in an airtight container (probably best left to >Apple to design it right into the original product, but you don't have that >option), and that way, no dust gets sucked in through the floppy. Doesn't >fix the problem of general dust, but that's more easily dealt with. This isn't exactly cosmetically apealing, but you could try tapeing an index card over the disk drive slot, so that the tape acts as a hinge. Just lift the card when you need to insert a disk. Alternately, some of the security devices that allow you to lock up your disk drive may also be able to keep dust out. -Reed
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) (08/27/90)
In article <1990Aug26.220310.1263@cs.umn.edu> aslakson@cs.umn.edu (Brian Aslakson) writes: [much discussion of psycho-thermodynamics... deleted] >Other people out there, don't reverse your fans unless you are an engineer >for Apple, or are rich enough to buy lots of Macs (including one for me :-). On what basis do you make this statement? Appeal to authority? The "quiet fan" replacement discussed here long ago (replacing the normal fan with a Radio Shack fan) has, as a side effect, a reversal of the air flow if you put the fan into the machine in the obvious way. I deliberately reversed the flow on my Mac IIx when I started using the Kensington stand, so that the forced flow would aid convection, rather than fight it. I have seen no problems reported on the net, and my own machine has no problems. There is certainly less dust in the floppy drives. Next, I suppose someone will tell us that disks should rotate the other way in the Southern Hemisphere. Marc Kaufman (kaufman@Neon.stanford.edu)
kent@circus.camex.com (Kent Borg) (08/31/90)
In article <2135@ux.acs.umn.edu> clarson@ux.acs.umn.edu (Chaz Larson) writes: >In article <8999.26d534ec@rsmas.miami.edu> miller@rsmas.miami.edu writes: [They both write various reasonable things on whether reversing a fan on a IIc_ is a good idea. Sounds like they agree by now.] Forgive me for tossing fuel on a dying fire, but I have another consideration: Aerodymanics. Suck air out of a cluttered box and there are going to be some eddies and back waters (back airs??), places that don't cool as well as others. Reverse the fan, blow air into the same box, and there will different hot-spots. Are we sure Apple didn't lay things out with those hot spots in mind? (I suspect that miller@rsmas.miami.edu is right, that the differences are within safe tolerences--but remember the Plus which ships out of the safe zone. No room for extra heat in a Plus!) Yet another thought, after a year or two of blowing dust through your computer things are going to become covered with an insulating fuzz of dust. This will help keep things warm. A reversed, filtered, fan would help this aspect. A final thought (I promiss): What fails first in these IIc_ machines? The power supply or something else? If it is the power supply reversing the fan might help over-all reliability, if it is the other, it would hurt. -- Kent Borg internet: kent@camex.com MacNet: kentborg AOL: kent borg H:(617) 776-6899 W:(617) 426-3577 "Congress was about to scuttle our defense department ... Could our military industrial complex be backing Iraq?" - my mother, 8-4-90
ireland@ac.dal.ca (08/31/90)
I've been following the reversed fan discussion and was surprised recently when I put my hand on over the vents on the left side of my MacPlus. It was quite hot. The author of the "Macintosh Repair and Upgrades" book recommends putting fans in Plus's, but says that one can also blow air over a plus with a house fan to cool it. This works amazingly well. It's barely warm now. But I'm wondering which side of the mac I should put the fan on 8:) . Keith