[time-nuts] HP 5065A rubidium lifetime

[J. L. Trantham]

Chuck,

Can you provide any other information about this repair?

How much disassembly of the RVFR, what kind of prep of the lamp casing, how
much wire, where did you find the wire, did you 'bend' the wire into a
'hairpin' or did you wind two wires then short one end and feed the power
from the other end, what kind of prep for the outside cylinder, what kind of
'jig' to hold everything in place while applying the urethane foam, etc.,
etc.

I have two of these and one arrived dead after which I 'killed' it some more
with a total melt down.  If this should arise again, a repair guide might be
very helpful.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Chuck Harris
Sent: Saturday, March 20, 2010 7:35 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 5065A rubidium lifetime


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

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