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Power Macintosh 6500/275 - variable fan speed?
Posted by: ry755 on 2022-09-01 16:10:50
I recently got a Power Macintosh 6500 and after playing around with it for a little bit, I could've sworn I heard the fans ramp up and down every now and then. But as far as I know, these older generations of Power Macs don't support variable fan speeds, right? The reason I'm curious about this is because if this computer in fact *doesn't* support variable fan speeds, then I'm worried that this might be a sign of a failing power supply.
Posted by: Powerbase on 2022-09-01 18:15:39
Which fan sped up? The CPU or power supply fan? Might just be a bad fan.
Posted by: ry755 on 2022-09-01 19:29:03
I'm not quite sure honestly, it's hard to tell. I would assume the power supply fan would be the louder one since it's larger.
Posted by: Powerbase on 2022-09-02 11:32:08
Probably needs lubricated or replaced probably. I dont believe those fans were variable.
Posted by: Phipli on 2022-09-02 11:37:17
It can be caused by something blocking the airflow, varying voltage or a worn out fan.

I'd stick a multimeter on the 12v (a molex?) and watch it while running a disk benchmark. Does the 12v dip?

Interestingly, some older macs had variable speed fans. Some fans had built in temperature sensors. I think the IIfx fan might be variable speed?
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