Info-Mac

I have a Power Mac G4 Mirrored Drive Door. My stock fan is DELTA AFB1212SHE 120mm X 38mm 150 CFM FAN 6942, 3700 RPM, 53dBA.

I am looking for a computer fan to buy, what are these term mean?

1) CFM (I know it has something to do with air flow power, lower number the better or higher number the better? )

2) RPM (I know it has to do with power? or how fast it spins, the lower the number better or higher the number better ?)

3) dBA (I know it has something to do with the noise, the lower the number more quiet I guess?)

Now, my factory original is 150 CFM, 3700 RPM and 50 dBa.

I am looking for quieter, yet provide same or better air flow and power. What do I look for ? which one of the following is the best pick and why ??

a. 96 CFM, 2400 RPM, (dBA unknown on this one)
b. 133 CFM, 3000 RPM, 45.90 dBA
c. 120 CFM, 2900 RPM, 44 dBA
d. 110 CFM, 2500 RPM, 45 dBA

Hey bulldog,
CFM = cubic feet per minute, the airflow, the higher the better.
RPM = rounds per minute, the fan´s rotation speed. Slower fans are supposed to be quieter.
dBA = sound pressure at metering curve (A), the lower the better.

So, b. would be my choice, if any.

The dB scale is logarithmic, a reduction of 3dB gives you roughly half the noise.
I dont see a 150CFM fan in your little chart, are you sure you want to reduce that?
Best wishes!

24bit wrote:Hey bulldog,
CFM = cubic feet per minute, the airflow, the higher the better.
RPM = rounds per minute, the fan´s rotation speed. Slower fans are supposed to be quieter.
dBA = sound pressure at metering curve (A), the lower the better.

So, b. would be my choice, if any.

The dB scale is logarithmic, a reduction of 3dB gives you roughly half the noise.
I dont see a 150CFM fan in your little chart, are you sure you want to reduce that?
Best wishes!

Thank you so much for your reply, I was thinking of the same answer, b, however, do you have any recommendation for replacement fan for my Power Mac G4 120 mm fan ? I can go with used OEM, but they are very noisy and I was thinking since I am going to replace it, I would like to find something quieter.

Sorry, I can not recommend anything, as I don´t own a G4.
The NB-Multiframe® MF12-P looks promising with 12 to 29 dBA, but i don´t know whether it will blow enough air.

Hi again, I just received my replacement fan for my Power Mac G4. (I have a Power Mac G4 Mirrored Drive Door. My stock fan is DELTA AFB1212SHE 120mm X 38mm 150 CFM FAN 6942, 3700 RPM, 53dBA.).

This stock fan quit working on me one day. I was told the fan had died. So, I have researched to find a replacement fan. Now........

When all were plugged in, the brand new replacement fan still did not work. What may be the problem ? I thought may be the motherboard was shot, (the connector on the motherboard was shot), but when I plugged in my smaller fan that sits on inside the computer cabinet door, the fan instantly run with no issue. So now I know that the connector on the motherboard is fine.

When I connected my brand new replacement fan to the smaller fan's connector, it did not run either. Now I am stuck with this. what do you recommend ? Is there any way to test that my brand new fan is in fact defective ? ( I doubt it ... )

A lot of times those fans come with an adapter to simply plug it into the disk drive power cable. If yours came with one of those, perhaps give that a try.

If it still doesn't work then you probably just got a faulty fan from wherever you bought it from. There isn't any reason it shouldn't work.

Also, only one topic for this is really necessary.

Turboladdade wrote:A lot of times those fans come with an adapter to simply plug it into the disk drive power cable. If yours came with one of those, perhaps give that a try.

If it still doesn't work then you probably just got a faulty fan from wherever you bought it from. There isn't any reason it shouldn't work.

Also, only one topic for this is really necessary.

Hi, yes adopter came with the Fan, 3 pin to 4 pin connector was included which had NO USE for my Mac, therefore, I did indeed bought 3 pin to 2 pin connector of course. Like I said, when ALL were connected, the new fan did not work.

Goodday,

You want to replace a air displacement fan for your mac. What the previous writer states is largely true, except that dB A stands for logrithmic Audio measurements represented by measurements with a Volume unit meter. And the dB unit for measurement of real sound is dB Spl (sound pressure level), sure the lower the noise of the fan, the better for your experience, but other factors are important also.

There is something else you must consider, there are several ways of driving a motor of a fan, some fans use a rotating magnetic field of flux, and a stationary magnetic field armature, which ostensibly means the fan is brushless. Brushless fans are more acceptable to this application. But is the fan DC or AC, being driven from an oscilator circuit?

I suggest that you examine the parts of Delta fans, and obtain the replacement fan with correct orignal part number, and assuming that the original part is the one you quoted, then the DELTA AFB1212SHE 120mm X 38mm, must be the right part number to ask about.

Do you have reason to suspect the fan has been changed before? If that is the case then you should consult the technical references for your machine to obtain the correct preferred manufacturer part number. Also when fitting the device, there is usually an arrow which indicates the direction of air flow, (just in case you can't tell the difference, between the suck and blow aspects, the build up of dust on the old fan will indicate which direction the fan worked in, and the new fan should be fitted so the air flow follows the same route.) I have known people use computers with two fans in them, and fit both fands so they blow air in from outside, into the case on both fans! Usually you suck air from the lower area, and blow it out of the top. Usually you blow air out from the power supply unit, and suck air in through the other fan. It all depends on where the heat is, what is hotter, and what kind of structure their is in the design of air flow.