Re: Physical planning info for 9406-720...

[Larry Bolhuis <lbolhuis@xxxxxxxxxx>]

That IS the internal cooling fans lighting off (to use the Turbine 
analogy). Those babies start up at full speed (30v or so) until they all 
check in. Then they 'downshift' to maybe 16 to 18v and run lots quieter 
unless another fan fails or the system senses the need for 'enhanced 
airflow'.  Not all the fans are the dual speed ones but the ones in the 
power supply area are.

I have several of those fans and if you connect them to the full rated 
30v they don't even sound safe! Check out the pictures of the original 
Frankie at www.frankenseries.com and that's what we have on the front of 
the 'external disk' units. In fact at COMMON in Indy, where those pics 
were taken' we had to rewire the fans from 24V down to 12V because they 
were simply too noisy for the certification lab.

 - Larry

Haase, Justin C. wrote:
> Anyone know what the noise is that the 620/720 systems make about 5
> seconds after power-on?  Sounds like some sort of turbine inside of the
> machine.  It can't be the fans - can it?? 
>
>
> --
> Justin C. Haase - iSeries System Engineer
>
>