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[Syn-Fi]

hi,
still stable but i've been thinking.  The problem with the G4 MDD and cooling is that there is no inflow of air but lots of outflow.  The front, bottom lip is the only area where there is some intake but nothing to drag air in.  Two Pancake 60x60x10 fans would fit there and you can get these 'breakaway' rubber mounts to fix them there.  With air coming in through the bottom the whole cooling situation would improve.

I'll write back when i've tried it.

[DieHard]

Sounds good, please include Mod photos

[macStuff]

has anyone experimented with alternating the direction of the two fans located within the powersupply to be in a push/pull configuration? rather than both pushing outward?

[DieHard]

has anyone experimented with alternating the direction of the two fans located within the powersupply to be in a push/pull configuration? rather than both pushing outward?

Heat rises, G4s run hot already, so any extra CPU/memory heat and all heat generated from add-in cards exits thru the PS.

I think the main theory is to flush all internal hot air (that the main center case fan does not take care of) out via the PS, so yes the air going thru the PS is already much warmer than the outside ambient air... now, a "push pull" maybe an interesting idea...

The fans in the PS at the top of the PS should always be exiting, the upper most area of the case (heat rises), but maybe the bottom PS fans could bring cool air in, that would exit thru the main fan and create a cooling circle, I am no engineer...lol   Also, I am no sure if there would be a cancellation effect if no baffle is put horizontally separating the PS in 2 halves.

[GaryN]

To all budding thermodynamics engineers here:

Experiment all you like with different fans, reversed-flow fans etc. but you had better have replacement parts / assemblies on hand to replace the stuff you fry in the process. There are specific reasons for every single little hole and vent cut into the chassis and the direction and flow of every fan. Some of the best-paid brightest engineers in the world work for Apple and you think not one of them thought about reversing a PSU fan to make a "push-pull" setup? Are you kidding?

If you stop and think for a sec, you'll quickly realize that reversing one of the PSU fans will simply cause the airflow to go around and around in a circle through the fans, never reaching the rear of the unit (where most of the hot stuff is) and the PSU will overheat faster than you can say "BTU".

In addition to the four obvious openings and the bottom slot in the front of the MDD, there are lots of little air holes punched into the sides that allow the PSU fans to draw cool air from the bottom between the steel inner frame and the plastic outer covers. Cool air enters the bottom, flows up through the space between the covers and chassis, is drawn into the PSU fans then is (and this is important) forced through the length of the PSU, exhausting hot air out the back of the computer along with the hot CPU air from the main fan.

>>>>>>  Cool air IN bottom front……hot air OUT top rear.  <<<<<<<

All of this is covered up by the motherboard, the drive cages and the PSU itself, but strip an MDD down and you quickly see there's a method to the madness, with carefully laid-out air passages feeding the fans with the intakes and outflows as far apart as possible to keep the inflow and outflow separated to discourage warm exhaust from finding its way back to the intake. Even the little fan in the door has a specific role, drawing air up through the side to cool the optical drive(s) compartment.

With the access door closed, the main fan has its intake well isolated from the interior and draws almost 100% outside air blowing directly across the CPU heat sink and out the back. Virtually ALL of the CPU heat is exhausted right out that way. Additional heat from additional PCI cards does accumulate inside the upper region but realistically, except for some video cards, most PCI accessory cards are not notorious heat generators. If you're concerned about the interior overall temp of the MDD, an effective solution is one of those little mounts-in-a-PCI-space fans. They're perfect for this job in an MDD, providing a little more general exhaust flow out the very top rear of the computer.

Lastly, let me remind all that aiming an IR temp reader at the PSU tells you almost nothing. It's NOT the outside that matters, it's the temp of the switching transistors themselves and there's no way to measure that during operation with an IR from the outside.

[refinery]

Even the little fan in the door has a specific role, drawing air up through the side to cool the optical drive(s) compartment.

If you have two optical drives in your machine, that side fan is completely and utterly uesless. The drives block the vent holes in that frame once theyre installed.
I found my MDD cooled much more efficiently once i decided to completely remove the optical drives and that frame. I can do 99% of what i need with disk images across a network and the remaining 1% of the time i just use an external.

[GaryN]

If you have two optical drives in your machine, that side fan is completely and utterly uesless. The drives block the vent holes in that frame once theyre installed.

You have noted what does appear to be an oddity. True, with two CD or DVD drives in the cage, the side air holes are completely blocked and that side fan accomplishes little. I wondered about that too until one day I bought an early version MDD and found the cage had one CD-ROM drive and one Zip drive. The Zip drive is much smaller and does NOT block the air holes. I realized adding a floppy drive in that space would also allow continued airflow. It then occurred to me that most if not almost all MDDs shipped with only one CD drive and many of them probably stayed that way.

I have both optical spaces filled in mine and you're correct - the little fan appears to accomplish almost nothing with two of them in the way. I thought about just disconnecting it but it makes almost no noise at all so…ehhh

Actually, my MDD is completely full but for one PCI slot. Remarkably, even with four HDDs, two optical drives, audio interface PCI, USB2 PCI, SCSI PCI and a Sonnet CPU, it still manages to not overheat. The "wind tunnel" may be noisier than some, but it does allow you to pack a lot of hardware into a reasonably-sized chassis without cooking everything.

[Bolkonskij]

Sorry for resurrecting this thread, but I don't think I need to open up the 2156th thread on MDD noise.

My MDD is still stock (AcBel PSU) and it does get annoyingly noisy. I got a backup MDD and upon inspection, I saw that it has a Samsung PSU and the Papst fan. After reading this thread, it seems that is Apple's later "silenced" version of the MDD.

Now since I don't feel too good about opening up a PSU to tinker with it and adding new fans, I wonder - is it worth swapping the big fan and the PSU in order to get the machine more silent? Anyone tried and can tell me if the difference is worth the hassle?

[GaryN]

Clearly, there is a significant improvement with the later one. Apple even offered the Samsung and Pabst fan as a free kit for a time to "silence" some very loud purchasers  of the original MDDs. You know they obviously had some highly-paid engineers measure the noise with expensive sound level meters when they acknowledged it was a problem.

Which begs the question: You bought a "backup" MDD. Does it run? It would seem YOU are in the uncommon position of having TWO complete machines with which to do a "before and after" comparison.
With or without a sound level meter, our ears will tell you if the difference is worth it.

We anxiously await the results of your evaluation……

[FBz]

Have an iPhone or an iPad? Download free app called “Decibel X” (or similar) and measure dB from same distance / position from both MDDs.



Short answer to your query: It depends on just how noisy and what kind of noise you’re talking about.

Is your backup MDD quieter? If so, how much quieter? Quiet(er) enough to warrant switching out the PSU with your “noisier” one? Screenshot your results and post along with distance / position notes and others might compare theirs in a similar fashion?

Once you’ve opened a PSU - it’s not really that difficult to switch out the two small PSU fans… IF they are actually the primary source of the noise. But first, you might try momentarily disconnecting the largest (case) fan from power and then booting and allowing it to run for a minute or two, just to see if that might be the actual main source of the noise. If it is, then it’s relatively simple to switch out that large fan.

Often however, a thorough and careful cleaning of all fans and fan blades… coupled with a small drop of light machine oil (allowed to soak into the fan bearing / bushing overnight) will reduce noise substantially. *Normally, access to the fan shaft bushing / bearing is underneath the sticker placed in the center of the back of the fan. Place fan face down overnight to allow the lubricant into and around the bushing. NOTE: only a single small drop is necessary and any excess remaining after overnight should be removed before re-installation.

And if you use high compressed air to blow-out the fans - be certain to restrict them from turning… as the compressed air may spin them faster that they were ever designed to rotate… and quite possibly damaging them in the process.

Syntho offers a great how-to post on replacing fans beginning this thread and GaryN, DieHard (und others) offer great insights here as well.

[Bolkonskij]

Thanks a lot for the helpful replies, guys!

Yes, the second MDD should work, but it wasn't powered on for two years. So got to check first. It was when I got fed up with the MDD going into "Windtunnel mode" again that I seached the forums, found this thread and learnt that there were actually two versions of the PSU / fan ... (wasn't aware of it)

The biggest noise comes from the two PSU fans, no doubt about it. I regularly clean my MDD with a can of compressed air to get rid of whatever dust is inside. I agree it makes a difference and should possibly always be the first step, but has already been done in my case.

About testing the noise of both machines - I'm concerned that it will be very difficult to achieve objective results as that would require generating the same circumstances for both machines. (using programs for the same time / same workload, having the same room temperature et al ... )

For now I'm going to look after the 2nd MDD and see if it works. If so, I'll have it run and will highly subjectively decide if it is noticably less noisy. I'll report back later with my impression - thanks so far!

[Jubadub]

If using HDDs, especially in quantities greater than 1, is a Power Supply and Temp. concern, one of the greatest MDD durability and noise upgrades you can make is to replace your HDD(s) (which is/are also likely to be 3.5" in size) with SSD(s). Considerably less energy drawn from the PSU, and thus less heat and more silence from it. You also gain bonus silence points for using a drive without moving parts (no HDD noises).

MDD goals.

[sequencers.io]

Given the Everflo F126025DH has not been manufactured in over a decade, and there's been at least incremental advances in fan quieting, any recommendations for suitable G4 MDD PSU fan replacements? I'm not sure what specs I should be looking at outside of 60mm 32CFM. I suppose I'd want a quieter rating than 31dBA as well, 12V and no PWM. I've been reading, and maybe I missed it but are there specific dimensions I should be looking for?

[IIO]

i always see only mm*mm and voltage as specs. but what about the effectivity? you dont want to replace a fan with one which is more quiet but also cools your components less than the original.

[Gaz]

I've just replaced the fans in my ACBell PSU with a pair of  Noctua NF-A6x25 PWM, rated 17,25 CFM each, that should be enought for cooling!  Noctua has top quality stuff!

[Bolkonskij]

And how is your MDD doing @Gaz ? Do the Noctua NF-A6x25 keep things cool with your MDD? Still looking into replacing my PSU fans.

I've since replaced the AcBel PSU with the Samsung one. Conventional wisdom is the Samsung PSU is quieter because it's 2nd gen (from what I read). So from my highly-subjective standpoint - the AcBel one is loud. The Samsung one is loud. I don't notice any difference. I'm not an audiophile, so my ears aren't as "tuned" but to me, it's all the same. Fans keep cranking up like crazy during heavy work (e.g. working with video) only to spin down for a moment and then starting again.

[DracheMitch]

Action Retro on YouTube replaced the MDD power supply with a small form factor 500w ATX unit, and there’s a guy on eBay who sells the power cable adapter for the motherboard.

The main cause of heat and noise in the MDD is the power supply.

I’ve got my parts on order and I’m going to do the same.

[coachla]

Step 1: Abandon the Apple MDD I'll-Be-First-To-Conform fashion mentality whose case design is absolutely useless but for a pair of earrings on the Jolly Green Giant.

Step 2: Think out of the box, and REMOVE the box!

Disconnect mobo fan lead which also causes RF in the system audio. Run one stock CPU fan and one stock PSU fan both at 12+5=7 volts. Photo is of three linked 1.25 dual MDD's running cool and quiet as a mouse.

Be done with this issue.

http://macos9lives.com/smforum/index.php/topic,5158.msg37202.html#msg37202