[time-nuts] HP 5065A rubidium lifetime
Bob Camp
lists at rtty.us
Sat Mar 20 15:44:58 UTC 2010
Hi
A bit off topic, but here it is anyway.
If you pull the bulb from a "dead" FRK rubidium to replace it, most are indeed black. The replacement bulb is nice and clear. A FRK is not a 5065 and the "stuff" in the bulbs is likely not exactly the same soup of buffer elements.
Bob
On Mar 20, 2010, at 4:08 AM, Bill Hawkins wrote:
> Corby,
>
> What I meant by "darkening" was that the photocell current and the
> second harmonic were at half of their minimum value given in the manual.
> I don't know what happens in the RVFR to cause that.
>
> Why would a clear bulb have a low output? Can you refer me to something
> to read? I haven't found the right words to get Google to reveal any
> useful links.
>
> Several years after I bought the 5065 in 2003, there was not enough
> second harmonic to maintain control, saturating the integrator. So I
> followed the cure for cell flooding given in the manual. After 10 days
> the second harmonic stopped improving at about 10 on the meter.
>
> Something appears to be microphonic in the photocell. A sharp tap to
> the case causes the second harmonic to peg the meter briefly. A Tracor
> 308 does something similar, but it doesn't have a meter for anything
> but error - the red Unlocked light comes on briefly.
>
> Perhaps my brain is darkening with age . . .
>
> Bill Hawkins
>
>
> -----Original Message-----
> From: Corby Dawson
> Sent: Friday, March 19, 2010 4:11 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] HP 5065A rubidium lifetime
>
> I have been repairing HP 5065A for over 20 years and have never had a
> failure due to "darkening"
>
> I did have one Efratom unit years ago that the lamp envelope had darkened
> so much it was unusable.
>
> Not sure if the is the "darkening" referred to?
>
> The "killer" 5065A failures are oven failures that melt the insides, and
> a bulb that has a very low output. (The bulb envelope is still nice and
> clear in these cases.)
>
> The bulb can be replaced with some Efratom ones with varying results.
>
> Also cell flooding can occur after long storage and/or storage in high
> temperatures.
>
> This is easily cured by applying 5VDC thru a 5ohm 10watt resistor to the
> TED (thermoelectric device) in the receiver for 6 days or so.
>
> Corby Dawson
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