[time-nuts] Z3805A cooling requirements?

[Volker Esper]

Indeed? I didn't expect that. There are people who say, that the control 
loop of OCXOs is optimized for still air and no additional cooling at all.

Said told us, that...

 >...a fan is about the worst thing you can do for your Z3805 it will
significantly worsen the stability of the output frequency...

Since the main task of the OCXO-oven is to stabilize the internal 
temperature, I can't imagine, that it get's into trouble when not 
externally cooled!?

If I'd ventilate the air around the OCXO case the heater had to work 
more and the power dissipation would be greater.

Am I wrong with taht?

Volker



Am 16.12.2012 15:35, schrieb Bob Camp:
> Hi
>
> By far the most common way to test and certify OCXO's is in moving air. It's rare to see one get in trouble from to much ventilation. The more common problem is thermal runaway due to inadequate ventilation.
>
> Bob
>
> On Dec 16, 2012, at 7:57 AM, Volker Esper<ailer2 at t-online.de>  wrote:
>
>>
>> Steward,
>>
>> What is the intended and what is the actual supply voltage? Which current is the unit consuming?
>> When we know that, we can compare the power consumption with our units. If it is in the same range, it should - with a little luck - be working properly.
>>
>> My two units are intended to be supplied by 19.5 to 30 V. I use 24 V and the Z3805s draw 0.9 A each. If I increase voltage the current decreases (typical for the switching supplies inside the Z3805).
>>
>> I don't cool the units, they just lie on an old electronics magazine (for not to scratch the case of my signal generator, lying below the magazine), so they can freely convect their heat.
>>
>> Cheers
>>
>> Volker
>>
>>
>>
>> Am 12.12.2012 01:21, schrieb Stewart Cobb:
>>> This may be a newbie question, but I'm a newbie, so:
>>>
>>> Do the HP telecom GPSDOs (Z38xx) require external airflow for cooling?
>>> They don't have built-in fans, but they sorta look like they depend on a
>>> rack-level cooling fan, which a telecom rack would almost certainly have.
>>>
>>> I ask because I bought a Z3816 awhile back which worked for about a week
>>> and then failed. I traced the failure to an internal power supply brick,
>>> which had a big finned heat-sink attached but nevertheless smelled
>>> overheated and was shorted internally.
>>>
>>> I never found a replacement power brick, and I don't have time to mess with
>>> it right now, so I recently bought a Z3805A. It, too, looks like it's
>>> working, but it started to feel awfully warm after a few hours, so I
>>> unplugged it for now.
>>>
>>> It probably wouldn't take much of a fan to bring the internal temperature
>>> down close to ambient, and the fan could be powered easily enough from the
>>> supply rails. But that might create a temperature gradient where the
>>> designers didn't intend one. Or it might cause problems I don't even know
>>> about yet.
>>>
>>> At the moment, the Z3805A is in a fan-less 19-inch rack with a bunch of
>>> other equipment, in a lab environment. Should it have its own fan?
>>>
>>> Cheers!
>>> --Stu
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>>
>>
>>
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