[Tfug] 90mm fan

[erich]

OK,
        Thanks guys. I just checked and the old fan is clearly 2-wire.
So, if
there is any speed variation, the PS must be tweaking the voltage.
         Yeah, I've seen HS kids with their souped-up video game boxes.
That's who buys the LED-studded fans.

                                                                                                  
Erich
Adrian wrote:

>On Sunday 26 November 2006 22:29, erich wrote:
>  
>
>>    I have a Compaq power supply that's giving out or, more precisely,
>>its fan
>>is making noises that suggest its days are numbered. Unfortunately this
>>fan is 90mm,
>>and I had to go out on the internet to get one.
>>     This PS has ACPI with thermal sensing that causes the fans to "rev
>>up" when the computer
>>it powers is "hot on a job". Is there something I missed in the
>>specification of the replacement
>>fan? I'm wondering if all fans run at variable speed or do you need
>>special ones  that
>>"rev up" when the power demand rises.
>>
>>    
>>
>
>You really need to pull at the existing fan, lookthe part number, and look at 
>the number of wires going in... There are basically 3 different types of 
>fans, with several variations of each:
>
>1) A "standard" 2-wire static speed fan, say like 12V DC 4500RPM. It may or 
>may not be "speed-regulated" by the motherboard/PS by reducing the fan's 
>supply voltage, i.e. the PS reduces the supply to 10V so the fan runs quieter 
>and only turns at 3000RPM... But either way the fan is the same.
>
>2) A "monitored" 3-wire fan. This is a fan that the motherboard/PS can monitor 
>the fan status on. They come in 2 basic types (though there are a number of 
>odd, one-off variations): RPM and rotor-lock. RPM is what it sounds like... 
>sends out a pulse every nth revolution to indicate it is alive. A rotor-lock 
>sends out a high signal constantly (or a low depending on the model) while 
>the fan is turning (ie. a "good" signal, not an RPM indication) and the 
>reverse when the fan rotor is jambed. Like #1, the speed can be adjusted by 
>the system lowering the voltage, but it system does it.
>
>3) A "monitoring" 2 or 3-wire fan. This is a fan that either has a thermal 
>sensor built into the frame (typically, though not always 2 wire), or a third 
>wire that goes to a special motherboard sensor, and the fan itself 
>dynamically adjusts based on the input.
>
>Many of the supposedly "super quiet thermal" fans, that you put in a drive 
>bay, or other aftermarket chromed neon blinky waste-o-money things are going 
>to be a #3. The typical newer 3-wire processor fans, that plug into the 
>motherboard, are #2, nearly always a RPM fan. (You typically find the #2, 
>rotor-locked variety in switches/packaged equipment). And most PS supplies I 
>have seen use the #1 type.
>
>As to what yours is?... I would guess a simple #2 with sort sort of adjustment 
>built into the PS circuitry itself, though you should check the fan model 
>number to be sure.
>
>
>Adrian
>
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