[time-nuts] HP 5372A Fan

[Ed Palmer]

Yes, the fan is variable speed and it's 12V DC.  It's described in the 
motherboard section of the service manual on page 11-4 (pdf page 503).  
That's why I thought it was so odd that the fan is blowing cool outside 
air over the thermal sensor on the motherboard.  I guess they could have 
calibrated the system to work on the basis of ambient temperature 
variations, but it seems backwards to me.

Ed

Mark Sims wrote:
> Are you sure that it has a variable speed fan?   My 5372A has a pretty quiet fan and I have never tried to change it.  I am assuming that it uses the same 117V fan as the 5371A.  That thermal switch may be a power supply shutdown.
>
> I have a couple of 5371A's that are a different matter.   Utterly obnoxious fans.   I put in much quieter 12V fans.  I powered them with a separate wall wart module mounted inside the box with velcro.  I used Nidec Beta V TA450DC fans rated at 250 mA.   Again,  I checked the before/after thermal environment and found no changes.
>
> I have some even quieter NMB "Smartfans" with a thermal sensor.  They draw around 150 mA until the temp reaches 35C,  then they kick in at 750 mA and scream bloody murder.   		 	   		  
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