[time-nuts] FE-5680A heat sink

Leigh L. Klotz, Jr WA5ZNU Leigh at WA5ZNU.org
Mon Jun 8 22:10:01 EDT 2009

This device is a pull from a larger system, probably a cell site.  It's 
clearly designed to be mounted on something, as it has lots and lots of 
holes around the edge.  I suspect there's some thermal management that's 
missing.  The FEI sheet gives "typical" data for the 0-50C range, though 
presumably that's ambient temperature. 

I don't want to cool the physics package per se, but I do want to at 
least approximate what kind of thermal solution ought to be supplied.

Quite a few of these have been sold, and I've gotten good advice from 
others on this list about calibration.  I'd hoped that someone would 
have experience with the thermal management.

So far I've seen 
which shows (but doesn't describe) a heat sink on the bottom.


> I'm puzzled.  I admit that I don't have a lot of experience with
> Rb standards, but I do have a bit of experience with the HP-5065A
> Rb standard.
> In the 5065A, the entire physics package is enclosed in an oven.
> Assuming that your Rb is the same, and I believe it is, your plan
> to force the physics package to run at room temperature is just going
> to make the oven work harder in its never ending quest to maintain
> stable temperature.  If you monitor the current draw of the 5680A,
> you will probably see that it goes up when you put a fan on it.
> Sometimes, you just have to let electronics run hot.
> What did the manufacturer suggest?
> -Chuck Harris
> Leigh L. Klotz, Jr WA5ZNU wrote:
>> I've attached an SMA connector to my FE-5680A and built an external 
>> linear power supply with a TO-3 7815.
>> I ran the device today for about half an hour, and used an infrared 
>> sensing thermometer to measure the external case temperature.
>> It got up to 48 C externally in the physics package area.
>> I put a muffin fan on top and it brought it down to 38C but I don't 
>> think this is a good plan because I worry about the effects of the 
>> fan's magnetic field on the Rubidium system.
>> I found in my junk box a finned Aluminum heat sink that's exactly the 
>> same size as the FE-5680A and plan to tap it around the edges for 
>> 4-40 hardware to attach to the many screw holes.  Even so, this heat 
>> sink will be on the bottom, so the FE-5680A will have to be operated 
>> upside down for this to help.
>> Has anybody got good thermal management solution for this device?  
>> This is the one currently selling on eBay in the 25x88x125mm chassis.
>> Thanks,
>> Leigh.
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