[time-nuts] HP 5065A rubidium lifetime

John Miles jmiles at pop.net
Sat Mar 20 05:14:11 UTC 2010


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
>
> John Miles wrote:
> > One big favor you can do your 5065A is to check the ESR of the
> electrolytics
> > on the A11 oven driver board.  C23 and C24 were open on mine, as was the
> > other instance of the same 20 uF cap on the battery-charger
> board, and the
> > lamp driver assembly had experienced overheating to a point that was
> > sufficient to char a resistor and crack it open.  I'm not sure
> how, or if,
> > those two caps would cause total control-loop failure, but there was
> > apparently nothing else wrong with this unit that could explain the
> > overheating.
> >
> > -- john, KE5FX
>
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