[time-nuts] FE-5680A heat sink

bruce at ko4bb.com bruce at ko4bb.com
Tue Jun 9 02:00:29 EDT 2009

has high quality images of the 5680A and 5650A internal electronics.


>some light might be shed on the heatsink problem by reading the data  
>sheet for the LPRO 101 (Symmetricom)
>The units will have similar issues to cope with.
>The LPRO has temperature controlled lamp and filter, at different  
>temperatures above 80C.
>Its power consumption is shown in a chart and is reduced as the  
>temperature rises because the heating power needed becomes less.
>It must have a 17V internal series regulator, because total power  
>consumption falls down to the minimum of 18V.
>MTBF is listed as 380kh at 20C, 320kh at 30C, 253kh at 40C, 189k at  
>50C and 134k at 60C.
>These are values that you would expect for most solid state boards.
>My solution was to put the device onto a finned heat sink in an  
>aluminum box with a tiny 12V brushless fan, (40mm)
>which runs on 8 volts and is switched by a thermistor in the heatsink  
>to keep the baseplate at 40C.
>This seems to be a good trade-off with MTBF, and the 10 MHZ xtal will  
>run at a constant temperature of 40C + or - 0.05.
>I have not yet assembled the gear to measure how much its performance  
>is improved.
>cheers, Neville Michie
>On 09/06/2009, at 2:18 PM, Mark Sims wrote:
>> Also see my post from June of last year where I had measured the  
>> heat sink rise over ambient of several rubidium oscillators in free  
>> air...  the FEI-5650 was very close to it's operating limit if  
>> operated in free air and not attached to something:
>> http://www.febo.com/pipermail/time-nuts/2008-June/031695.html
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