[time-nuts] Rb cooling

[Bob Camp]

Hi

Yes, I have seen several Rb's die from what I believe were temperature
related causes. Since it's an accelerated MTBF sort of thing, *proving* they
were temperature related is difficult. 
Put another way - I believe the manufacturer's data on MTBF vs temperature
is fairly accurate. At elevated temperatures, the life of the device is in
the "few years" (2 to 4) range. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Chuck Harris
Sent: Monday, July 18, 2011 12:00 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Rb cooling

For all of this attention to cooling the oven on the Rb standards,
has anyone seen any failures that are attributable to heat?

I sort of doubt it.

-Chuck Harris

EWKehren at aol.com wrote:
> I monitor and fan cool the base plate, stays nice and constant at 45 C
> which I can not say with heat sink only. I am considering lowering the
base
> plate to 40 C. I have a heat sink on the base plate with the fan blowing
over
> it. Makes good heat exchanger. I have experimented with heat pipes from
Lap
> Tops  but never fit for mechanical reasons. May work with a LPRO's. Al my
> Rb's are  Efratom.
> A variable speed fan will reduce any ambient temperature influence. That
is
>   why I chose to use a fan.
> Use a dual Op Amp for temp. control. Nothing special. Fans are $ 3.00 I
> have monitored points inside the Rb's and they are within 1 C over time.
> Bert Kehren

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