[time-nuts] SMPS or conventional?

[Bob kb8tq]

Hi

The physics package is not really that different than an OCXO. It needs to hit this or that temperature. You 
derate the parts that go into the “hot zone” in order to hit a “reasonable" MTBF. Indeed, some manufacturers 
seem to do a better job in this regard than others. 

The parts on the rest of the device seem to be pretty standard stuff in the Rb’s I’ve torn open ( = lots of them ). 
The assumption seems to be that there will be cooling to keep those parts at a reasonable temperature. Since
the impact is to MTBF, it’s very much a “only time will tell” if they got it right. 

Bob

> On Nov 24, 2020, at 8:29 AM, 李 <bd4kc at 126.com> wrote:
> 
> I see, I've always wondered if the internal electronics are specially made because the modules are really too hot.
> Assuming a temperature increase of 10 degrees and the operating life is reduced by half, the module life should not be long.
> 
> 
> 	
> 李
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> On 11/23/2020 22:15, Bob kb8tq <mailto:kb8tq at n1k.org> wrote:
> Hi
> 
> There are two “zones” in the typical Rb physics package. They both need to be heated. Unfortunately they need
> to be heated to *different* temperatures. This makes for an interesting design. Insulate things to well and the one
> that is supposed to be at a slightly lower temperature is heated up by energy from the hotter zone. In addition, the 
> board with all the electronics on it ( or boards) are full of very normal electronic components. Their failure rate goes 
> up the hotter they get. 
> 
> Heat sinks do indeed help keep all of this in balance. The heaters are designed to get the physics package to the
> appropriate temperature from some very low point ( 0 or maybe -30C). They have *plenty* of reserve power 
> capability. In addition, they run at relatively low power (relative to their ratings) in normal operation. Optimizing 
> to reduce their failure rate while increasing the failure rate of a few hundred other parts does not improve the life
> of the Rb …
> 
> Bob
> 
> 
>> On Nov 23, 2020, at 7:33 AM, 李 <bd4kc at 126.com <mailto:bd4kc at 126.com>> wrote:
>> 
>> When the Rb clock is working, it needs a high temperature, isn't heat dissipation breaking the heat balance?Increased power consumption？
>> 
>> 
>> 
>> 
>> 
>> 	
>> 李
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>