[time-nuts] HP10811-60111 oven failure + repair

Sylvain RICHARD sr75pro at free.fr
Fri Oct 21 15:09:42 UTC 2011


Achim Vollhardt wrote::
> Fellow time-nuts,
>
> my humble HP10811 + Shera controller combo signaled loss of lock since 
> about a week after 5 years of non-stop operation. Frequency 
> measurement showed it to be ca. 90 Hz low and the added oscillator 
> enclosure (8mm aluminum case) barely exceeded room temperature. 
> Measurement showed oven current to be zero and after some Google 
> research, the thermal fuse for the oven controller became the prime 
> suspect.
>
> Opening the oscillator is rather easy due to screws, pulling the inner 
> isolation lid as well. With help of the service manual, the fuse is 
> quickly identified and proved indeed to be open.
>
> I had a 24V, 1.5A polyfuse at hand which was soldered in parallel to 
> the existing fuse. 1.5A seems a bit large, however I think some 
> derating is advantageous due to the elevated temperatures. Closed 
> everything and first connected the oven supply only:
> <snip>
> Regards,
> Achim
>
Achim,


You're not the first with this problem. Search the archives for tons of 
conflicting advice:
http://www.google.com/search?btnG=1&pws=0&q=site%3Awww.febo.com+%22thermal+fuse%22

-- 
Sylvain RICHARD




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