Re: 24" iMacs run hot!

In article
<replytogroup-54509C.22184107062007@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
The New Guy <replytogroup@xxxxxxxxxxx> wrote:

You hard-headedly refuse to admit that the temperature of the
COMPONENTS is what really matters, not the temperature of exiting air!

One day it will dawn of some of you that if the temperature of a
component rises and is not cooled with a heat sink, the temperature of
the exiting air will be hot. The trick to this problem is to cool
something with external air and by radiating the heat away from it as
soon as possible. Or in the case of the hard drive, its the hard
drive casing itself since we can't get air in there to cool the
components that are heating the hard drive enclosure. So that's why a
fan, using exterior ambient temperature air (not hot internal case
air) works so admirably. A fan blowing on to it, not sucking hot air
out of the case that just happens to wander past the hard drives.

There is another issue to consider. This has nothing to do with the original
subject. Namely, the temperature of exiting air is directly related to the
temperature of the room where the computer is located.

Yes - the 2 temperatures should be very close if the components are
cooled well. As soon as something is getting hot, its a sign the heat
sink is not up to the task. The same principle allows some heat sinks
to cool CPU's with no fans at all. Just the slightest airflow is
enough to whisk that heat away that is being radiated by all those
cooling fins of the heat sink. And it follows that if one put a one
of those large heat sinks, the air off that heat sink wouldn't be
warm. And of course you'll notice every good heat sink these days
uses heat pipes; almost all of them being expensive copper. So you
can see why a manufacturer tries to shy away from expensive parts like
that.

I have 2 macs in my rather large study that are on 24/7 and the room is
always warmer than it should be. In the winter I close all the heating/AC
floor registers and in the summer I open them + I have a ceiling fan. Of
course, the hard disks contribute to the heat as well.

What model of Macs? It should be possible to replace the heat sinks
in some models. Or by looking at the weakness of the design, one may
rectify it.

For instance the G4 tower (specifically a dual 500 but others might be
similar) can be cured so easily.
Disconnect the useless 4" fan.
Mount a 80 to 120 mm fan running at 5 volts (red and black wires off
your Molex multicolored white plastic plugs that power things like DVD
burners and IDE hard drives) so its silent, on the CPU heat sink.
That will cool the CPU heat sink well. Now take apart the power
supply and turn the fan so it blows in. Change the wires so its
running at 5 volts (red and black). Now it will be almost inaudible.
And it will be cooled much better now that you're not using hot
interior case air to cool the power supply heat sink(s). The only
downside to this scenario is you have to have the case open a crack to
let the heat escape. But as long as you don't have a lot of dust,
you're fine.

I forgot to mention that even though you're cooling the CPU heat sink
with warmed case air (not warmed much thanks to the opening at the top
for the heat to escape), this works better probably because the fan is
closer to the heat sink. As in right on top.

I saw a G4 tower 1.25 ghz the other day and the weak part of this
design was mounting the hard drives so the air passes by them before
being conducted to the CPU heat sink. Great for the hard drives, bad
for the CPU. It has provisions for 4 hard drives (maybe more) so just
don't use the ones at the bottom.

Fans have gotten much quieter these days so sometimes just replacing
an older fan with a newer one can reap huge benefits. Sleeve bearings
are the worst, single ball bearings are better, dual ball bearings are
best.
.

Relevant Pages

  • Re: Heatsinking a 3W Luxeon
    ... But the air has to flow freely, ... No need of forced air movement, enough surface of the heat sink in air ... change that *can* include a fan... ... why couldn't it cool down a 3W luxeon? ...
    (sci.electronics.design)
  • Re: Motherboard temperature.
    ... between the HDDs and the PSU (which has its own fan). ... I also have a Zalman CPU cooler with a fan that pulls air over ... the M/B. ... The M/B temperature is currently 50 ...
    (alt.comp.hardware.pc-homebuilt)
  • Re: Motherboard temperature.
    ... between the HDDs and the PSU (which has its own fan). ... I also have a Zalman CPU cooler with a fan that pulls air over ... The M/B temperature is currently 50 ... That gives the best possible cooling for the hard drives. ...
    (alt.comp.hardware.pc-homebuilt)
  • Re: 24" iMacs run hot!
    ... not the temperature of exiting air! ... out of the case that just happens to wander past the hard drives. ... cooling fins of the heat sink. ...
    (comp.sys.mac.system)
  • Re: Heatsinking a 3W Luxeon
    ... But the air has to flow freely, ... No need of forced air movement, enough surface of the heat sink in air ... change that *can* include a fan... ... "CPU", why couldn't it cool down a 3W luxeon? ...
    (sci.electronics.design)