[time-nuts] HP5370 power supply measurements

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Fri Jul 15 09:17:31 EDT 2016

On 13 Jul 2016 08:31, "Charles Steinmetz" <csteinmetz at yandex.com> wrote:

> An external fan blowing on the heatsink keeps my 5370s nice and cool, for
about $10 each.

So more noise.

> *if the counters were operated 24/7/365*.  I sometimes take data for a
few months straight, but very, very far from 24/7/365 on average.  So for
me, break-even would be more like 50 years.

I don't suppose Poul's main motivation is to reduce his electric bill.

> Speaking of fan noise -- you can't really get away with replacing the
internal fan with one that moves less air, so it is hard to find a
replacement that generates significantly less noise.  If you find one,
please share the make and model -- all 5370 owners would love to know.
> Best regards,
> Charles

Surely one of the main  advantages of the SMPS route is the higher
efficiently means less cooling air is required.  That means less noise.

I often here of people replacing fans with quiter ones, but I suspect that
all they really do is reduce the airflow. I believe that most of the noise
one hears is the movement of the air.  From what I have read, sleve bearing
fans make a bit less noise than ball bearings fans.  However,  although the
MTBF of both types is similar at 20 degree C, the MTBF of sleve bearing
fans decreases quite a bit with only a modest increase in temperature.


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