ATX PSU conversion Powermac G3

[ACD30"]

Update:

It's been some months since this old thread was sort of hijacked for the purpose of discussing replacement fans. ? I am actually revisiting this because I plan to retrofit a few other Macs in the near future.

I have not been using the PowerMac G3 Beige extensively, but I have since done a few 'gaming' sessions on it. From what I can tell, the system is running without a hiccup. Granted, I recently realized that the max CFM for the Arctic fan I bought is lower than the max CFM the original Sensflow fan is capable of. The Sensflow's CFM seems to have been measured with the fan at its resting RPM; however, this fan can spin as fast as 2447 RPM and can then move much more air than the Arctic fan can - about 86 CFM. Now, I don't think the Mac would have ever had the stock fan spin to max RPM... but, I do wonder at what RPM it would have been under the aforementioned 'gaming' load - as well as how much air it would be moving. We had discussed that the stock fan may have been overkill, but I'm still worried my Arctic fan may be under-performing for the Mac's needs. I also don't know if the Arctic fan is even running at full RPM. For all I know, it's resting below that and moving well less than 53 CFM. (The temperature diode should be doing its job, even with the fan converted to 2-pin - shouldn't it?) Could someone calm my doubts?

 

[TzunamiOSX]

I doesn't have the same fan like you, but i don't have temp problems. All is runnig well, also when cpu and gpu working at max.

The temp diode of the Arctic fan of the is working, but to get the max speed, the temp must be around 40°C on sensor.

Never heard the Sensflow speed up all the time. I think this was the standard fan for all cases at this time and has a to high airflow for G3s.

 

[ACD30"]

I doesn't have the same fan like you, but i don't have temp problems. All is runnig well, also when cpu and gpu working at max.

The temp diode of the Arctic fan of the is working, but to get the max speed, the temp must be around 40°C on sensor.

Never heard the Sensflow speed up all the time. I think this was the standard fan for all cases at this time and has a to high airflow for G3s.

Thanks for your reply. I believe it is around 40°C, for the highest speed setting on the Arctic. And although I was recently wondering whether or not the speed sensor was working, I remember that the third wire is simply for carrying fan data and nothing more. Thus, the diode should still be doing its job, even though I've converted the fan to 2-pin.

Regarding the stock fan config: I used to hear my G3 ramp up shortly after boot. I wasn't sure whether it was the Sensflow or the PSU fan. I don't see any reason that the Sensflow would have needed to ramp up, unless of course its parameters were super conservative. That having been said, it could have been the PSU fan all along... I'm not sure. With the Arctic fan in there, the PSU fan is definitely more audible; however, as far as I can recall, its RPM is constant regardless of the load.

 

[ACD30"]

Another update... I keep revisiting this — I know that.

User TznunamiOSX proved that their Mac was running cool after a fan replacement; however, depending on the model of Mac, fan replacement might not be such a good idea. Take a look at this article: it would turn out that CFM isn't the only specification to consider, but static pressure as well.

This reminded me of the fact that the G3 Minitower's fan tunnel is a right angle. I had thought it was strange, given it would presumably take a hefty fan to push air through it. After realizing the significance of static pressure, I now wonder if the original fan was loud for a reason; it may have had a higher rating in that category than the Arctic F12 I chose. (I would confirm this, but specs on the Sensflow don't include static pressure...) I do really hope that the Artic is moving enough air through that plastic dam.

I think the contents of the aforementioned article are worth considering, especially if your Mac is the type whose PSU's fan is the only active cooling mechanism in the entire computer. Thoughts? Again, I have little concern for certain newer models of Mac, such as Tznuami's heavily upgraded PowerMac; however, for example, a Macintosh SE or Quadra 900 may not be worth touching.

 

[TzunamiOSX]

Static pressure is a factor in some Computers. In the G3 the standard fan is running so low in all conditions, that you don't get a significant pressure.

 

[ACD30"]

Static pressure is a factor in some Computers. In the G3 the standard fan is running so low in all conditions, that you don't get a significant pressure.

The original Sensflow in my PowerMac G3 definitely seemed to ramp up with usage, but I can't confirm how much air it was moving. Looking at the blades, though, it would appear as though it can put out more static pressure than the Arctic fan can. I wonder if instead I should have purchased a high-pressure fan meant for this application.

 

[ACD30"]

For laughs, it would be interesting to take the original Sensflow fan and use one of the adapters to run it at 7 volts and see what the acoustics are like.

 

[TzunamiOSX]

For laughs, it would be interesting to take the original Sensflow fan and use one of the adapters to run it at 7 volts and see what the acoustics are like.

Because the original Sensflow is using a PTC-Resistor im nearly sure the fan ist not starting with a 7-Volt-Adapter and a room temperatur of around 20°C.