[time-nuts] 5680A what is a reasonable case temp ?

Bob Camp lists at rtty.us
Thu Mar 1 00:24:55 UTC 2012


Hi

If it is a normal FE it is pretty close at 15 minutes and quite good after an hour or so. It certainly will beat the original OCXO at at hour. You might just run it when the counter is on and forget about running it in the standby mode.

Bob



On Feb 29, 2012, at 1:15 PM, Chris Albertson <albertson.chris at gmail.com> wrote:

> That is one of the better uses for a 5680.  I have a counter that is
> non-function because some one salvd the HP OCXO from it and I'm
> thinking that a 5680 would fit inside.   But then I thought again and
> the 5680 can fit outside.
> 
> One problem I think with your setup is that the 5680' temperature will
> change abruptly when you take the counter off standby.   You might
> have to wait 15 or 20 minutes for it to be stable.    It think it is
> easy to just run the fan at the exact same minimum rate all the time
> I put a temperature sensor in the 5680 and use a comparitor to turn
> the fan off and on.  The 5680 needs 15 volts so I dropped some volts
> with an LM317 regulator  I adjust the regulator voltage so the fan
> does not make to much noise and the lm311 swiches the fan on/off as
> required.  So there is never an abrupt change.  and the fan run no
> more than it absolutely needs to.   I had to add a positive feedback
> resistor to reduce the cycle rate.
> 
> On Wed, Feb 29, 2012 at 4:15 AM, Peter Gottlieb <nerd at verizon.net> wrote:
>> I am fitting one of these into a HP 5335A counter.  The project became a bit
>> more involved than it first seemed and part of that is how to deal with the
>> cooling.  The manual shows an AC fan but it had been replaced (sloppily, I
>> might add) with a DC fan which was terribly noisy.  I found a much smoother
>> one with even more airflow in my junkbox.  The 5680A is mounted near where
>> the fan is so it gets plenty of airflow, but what about when the unit is in
>> standby?  What I did was put a little relay in which is powered by one of
>> the DC supply outputs.  When the unit is off, the relay opens which places a
>> resistor in series with the fan (which is now powered by the small laptop 15
>> volt supply I installed).  Thus, when in standby the fan drops to a lower
>> speed and acceptably quiet operation and the 5680A doesn't get too hot.  I
>> determined the resistor value experimentally via my super duper accurate
>> run-unit-for-a-while-remove-cover-feel-5680A-case-change-resistor-repeat
>> method.  Ok so I'm not looking for supreme accuracy of temperature, just
>> good operation.
>> 
>> Nifty little project to get great accuracy for half the price of a good used
>> HP oven oscillator.
>> 
>> Peter
>> 
>> 
>> 
>> 
>> 
>> On 2/29/2012 6:03 AM, Attila Kinali wrote:
>>> 
>>> On Tue, 28 Feb 2012 11:42:51 -0800
>>> Chris Albertson<albertson.chris at gmail.com>  wrote:
>>> 
>>>>  It's clear to me from seeing all those screws that
>>>> the 5680 needs to be firmly connected to some kind of heat sink even
>>>> it only a large plate.
>>> 
>>> It could also be that those screws are used to hold the top
>>> and bottom part of the cover firmly together. Dont forget that
>>> Rb's are sensitive to magnetic fields and that the case is mostlikely
>>> made of some high permeability material.
>>> 
>>>                        Attila Kinali
>>> 
>> 
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> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
> 
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