PowerMac G4 Fan, tamed by HD

[Greffe]

Hello,
I've had a puzzling experience with the old PowerMac G4 MDD, a noisy machine, and a recent external hard drive. When I connect the HD via FW800 or FW400, the fan noise is seriously reduced, and stays quiet until I remove it (still when the drive is ejected but still connected).
I've tested the temperature monitor with this and the HD seems to have little or no effect, so the fans are still apparently doing their job. If someone knows of a way to reproduce this quieter performance, at a configuration/settings level, without leaving the HD always connected, that would be awesome.
I've already enabled nap mode, and I think the G4 had its fans exchanged under the old recall program, but the noise level's still pretty high.

 

[MatthewLTL]

Hello,
I've had a puzzling experience with the old PowerMac G4 MDD, a noisy machine, and a recent external hard drive. When I connect the HD via FW800 or FW400, the fan noise is seriously reduced, and stays quiet until I remove it (still when the drive is ejected but still connected).
I've tested the temperature monitor with this and the HD seems to have little or no effect, so the fans are still apparently doing their job. If someone knows of a way to reproduce this quieter performance, at a configuration/settings level, without leaving the HD always connected, that would be awesome.
I've already enabled nap mode, and I think the G4 had its fans exchanged under the old recall program, but the noise level's still pretty high.

That is rather strange. I have a MDD (retired at the moment) and the loudest fans is actually the PSU fans. I actually modified all the fans in the PowerMac to run on a PC Fan Controller. I also added two exhaust fans behind the CPU which were also controlled by the Fan controller. The were PC fans so no modifying was needed. The controller also controled the two stock fans. Perhaps that is a option you can go with just place the controller in one of the drive bays.

 

[NathanJHill]

Off the top of my head, it could be as simple as your G4 needing to reset its PMU.
http://support.apple.com/en-us/HT1939

On a more serious side, it could be your power supply getting weak, but that is also a shot in the dark.

 

[Greffe]

Not sure about the PMU reset. The G4 performs normally, it's just always been a loud beast--until we got this external drive. I imagine it has to do with the power feed to the drive, which is the kind without its own PSU. With other external hard drives that have PSUs, the fans remain just as loud as ever.

 

[eyoungren]

Not sure about the PMU reset. The G4 performs normally, it's just always been a loud beast--until we got this external drive. I imagine it has to do with the power feed to the drive, which is the kind without its own PSU. With other external hard drives that have PSUs, the fans remain just as loud as ever.

That's kind of what I suspect.

The power draw from the PSU is enough to cause the fan to spin slower. A slower spinning fan is quieter, hence less noise.

You wouldn't know if it was spinning slower because that's not a quantifiable observation you can make short of actually seeing the fan blades barely moving.

While the fan speed is reduced it's probably not enough to change the internal thermal temps.

 

[Greffe]

That's kind of what I suspect.

The power draw from the PSU is enough to cause the fan to spin slower. A slower spinning fan is quieter, hence less noise.

You wouldn't know if it was spinning slower because that's not a quantifiable observation you can make short of actually seeing the fan blades barely moving.

While the fan speed is reduced it's probably not enough to change the internal thermal temps.

Do you think there's a way to set the fan to always spin slower, regardless of the connected drives? That's what I'm hoping...

 

[eyoungren]

Do you think there's a way to set the fan to always spin slower, regardless of the connected drives? That's what I'm hoping...

Not unless it's a variable speed fan.

You could always replace the fan itself. My Quicksilver is different than your MDD, but the inside fans are standard 120mm fans that you can buy just about anywhere.

I replaced mine with a 95cfm CoolerMaster that does about 2000rpm or so. It's got two separate cables that can reduce the fan speed if I were to plug them in. But even at 2000rpm that fan is considerably quieter than the stock fan I took out (and much more efficient).

The MDDs are notorious for being noisy. Replacing the fan though is an inexpensive way to reduce noise. The CoolerMaster I bought was around $20. But any generic type fan can be picked up for $3 or or so. Just depends how much money you want to throw at it.

 

[Greffe]

Fan replacement

Interesting. I think I've read something about this in the past, and had a vague memory of this involving either high cost or a difficult operation. I have, at one point, gotten the PSU out and looked at the fans, which required bending the case a little. Is replacement as simple as splicing standard fans in to the stock ones' wires?

 

[eyoungren]

Interesting. I think I've read something about this in the past, and had a vague memory of this involving either high cost or a difficult operation. I have, at one point, gotten the PSU out and looked at the fans, which required bending the case a little. Is replacement as simple as splicing standard fans in to the stock ones' wires?

Yes. Red to red, black to black. Some fans come with a third wire for speed adjustment based on thermal temps (as supplied by the logic on a PC motherboard), but that wire can be safely ignored.

However, some of these fans come with adapters that allow you to hook them up to Molex connectors. Or you can find adapters. That saves having to splice things.

The PSU is a little different in that you have to get it out, discharge the electricity from it, open it and swap out the fan. I've done that with my QS with some trepidation, but the replacement fan is of higher CFM and does the job very well.

You can be creative too if you like. The CoolerMaster I bought has blue LEDs in the fan hub. Makes for a nice effect.