[time-nuts] 5370A vs 5370B

[David Forbes]

At 4:10 PM +0000 3/10/10, Mark Sims wrote:
>Yes,  I replace the standard HP fan with a MUCH quieter one.   I get 
>mine from a local surplus shop.  It is made by AAVID.  it draws 120 
>mA at 12V and I  run it off the 10V supply (which is somewhat over 
>10V).
>
>Before getting all whiny about overheating,  careful HP engineers 
>putting that obnoxious hurricane in for a reason,  etc...  know that 
>I put several thermocouples all over the guts of the machine and 
>found no significant changes in cooling.   I have had modified 
>machines running continuously for many years.


It's reasonable to assume that HP engineers put in twice as much fan 
as needed by 95% of their customers, to prevent problems with that 
last 5% that run the thing in an extreme environment. If the 
counter's spec sheet says it will run at 50C, then it's gotta be able 
to run for a couple years at 50C without failure. So your 25C office 
can use a much quieter fan.

Our telescope at 3500m altitude, on the other hand, needs all the fan 
noise it can get since the thin air is only 50% as effective at 
cooling as sea-level air is.
-- 

--David Forbes, Tucson, AZ
http://www.cathodecorner.com/