[time-nuts] Power supply for 'Bay FE-5680A?

Bob Camp lists at rtty.us
Fri Jan 6 17:29:43 UTC 2012


Hi

I've been down this road with several Rb's. The answer is fairly simple.
They work fine with a hot base plate. They don't work any better or worse
with a hot plate than a cold(er) one though. 

The gotcha is that the MTBF of the parts in the unit is indeed impacted by
the higher temperature. Hotter = stuff fails faster. With no heat sink, you
will run fine for a number of months or even a couple of years. Then
something odd dies. It may or may not take other stuff with it. I'm a slow
learner and have killed to many Rb's this way. 

If you heat sink them, they do indeed pull a little more power in the
heaters. I have not seen one fail from overworked heaters when heat sinked.
There's nothing magic about the heat sink. A chunk of PCB material or a
scrap piece of aluminum plate can do the job.  

Most of the datasheets get around this by specifying base plate temperature
rather than ambient. In some cases the fine print that obscures that point
is pretty far down in the spec. Usually that gets taken as "hottest part of
bottom of the unit".

Of course with cheap Rb's you can toss one out when it fries and just
replace it...

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Chuck Forsberg WA7KGX N2469R
Sent: Friday, January 06, 2012 11:02 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Power supply for 'Bay FE-5680A?

The Tech Manual does not call for heat sinking (unless I missed something).
The top has labels over much of the surface.
The bottom has a plastic sheet between the circuitry and bottom plate.

It appears the unit was expected to be rather hot when running.
I have mine mounted on the out side of the box using standoffs.

On 01/06/2012 07:39 AM, Bob Smither wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Chris Albertson wrote:
>> On Thu, Jan 5, 2012 at 6:11 PM,<time-nuts at custodes.info>  wrote:
>>
>>> l<http://www.freqelec.com/rb_osc_fe5680a.html>  says 32W peak, but then
>>> also 15-18v at 700mA, which doesn't make sense.
>>
>> It will pull 35W for the first five or so minutes then the current drops
>> rather suddenly to about 700mA.
>>
>> I have an analog amp meter on my power supply and I can see a switch over
>> after the unit heats up.   They must run an internal oven heater full
tilt
>> at first then go into regulated mode.
>>
>> Some one else said you can cause the FE5680 to draw more power in steady
>> state mode by adding heat sinking it.  Yes that works.  Seems the FE5680
>> wants to be at some set temperature and the heat sink means it takes more
>> power to keep at the set point.   I just let the fe5680 rest on a small
>> aluminum plate.
> Have you measured the case temperature of your FE5680?
>
> I put mine on a heat sink and the case temperature stays around 50C.
Without
> the heat sink it was around 60C.  Does anyone know what temperature is
> recommended?  The 50C seems a little hot, but the unit appears to work
well.
>
> - --
> Bob Smither, PhD                                   Circuit Concepts, Inc.
> =========================================================================
>       Government is not healthy for children and other living things.
>         -- Jeff Daiell
> =========================================================================
> Smither at C-C-I.Com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)
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-- 
Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
   Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430

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