[time-nuts] External cooling fans - source

Charles Steinmetz csteinmetz at yandex.com
Wed Dec 20 20:01:24 UTC 2017


David wrote:

> For what it is worth, my 5370B run very hot, which forced me to check my
> mains voltage    *   *   *
> it was consistently high.    *   *   *
> I managed to get the supply company to reduce the voltage by 5%.

Eliminating that small amount of extra dissipation won't get you 
anywhere near the safe heatsink temperature zone with a 5370.  I tested 
one set for 120v with line voltages down to 90v (-25%), and the 
heatsinks were still way too hot for comfort (both for your hand 
touching them, and for peace of mind re: longevity).

> It would be interesting to know how low the AC input can go on a 5370B
> before the regulators fail to regulate.

The HP spec is +5, -10%.  That includes a safety margin.  -10% is not 
the absolute minimum (where the supplies drop out of regulation).  The 
one I tested down to 90v was still in regulation at that voltage, but it 
is possible the regulation might have been less effective at that 
voltage than designed due to lack of sufficient regulator headroom.  I'd 
say you're most likely fine down to -20% or so, but test to make sure. 
And note that there may well be some unit-to-unit variance.

Best regards,

Charles





More information about the Time-nuts_lists.febo.com mailing list