[time-nuts] HP 5065A rubidium lifetime

[Chuck Harris]

I can't say for certain.

The heating element is a single layer of formvar coated
nichrome wire.... about #36 gage.  To avoid magnetic fields,
they wound it bifilar, and shorted the far end of the bifilar
wires... forming a "hairpin" loop.

I found a short about 1 inch into the 5 inch winding, and the
oven driver transistor was open circuited.  The 1 inch that
wasn't shorted was surrounding the area of the lamp assembly.

I recall that the oven fuse was ok.

-Chuck Harris

John Miles wrote:
> What was the root cause of the oven failure in your case?
> 
> -- john, KE5FX
> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of Chuck Harris
>> Sent: Friday, March 19, 2010 9:58 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] HP 5065A rubidium lifetime
>>
>>
>> When my 5065A had its oven failure, it got so hot that it melted
>> all of the
>> solder joints on the lamp board.  I resoldered the joints,
>> rewound the oven
>> winding, and foamed the unit with some spray can urethane (Great
>> Stuff), and
>> had it working again for a couple of years.  Then something else failed.
>>
>> I'd sure like to fix it, but Scott McGrath, representing himself as an
>> employee of Harvard University, borrowed my manual more than a year ago,
>> and refuses to return it.  Oh well!
>>
>> -Chuck Harris