[time-nuts] Fw: cs beam tube failure???5071a tube is dead now...

[David Welch]

----- Original Message ----- 
From: "David Welch" <aceamusements at mchsi.com>
To: "Dave Carlson" <dgcarlson at sbcglobal.net>
Sent: Sunday, February 10, 2008 9:24 PM
Subject: Re: [time-nuts] cs beam tube failure???5071a tube is dead now...


> Dave..
>
> I did get a case # with agilent and they said to call symetricom and see
> what they would do?The guy I talked with did not know much about that
> division other than it had been sold but insisted they(agilent)only
offered
> a 3 yr. warranty..
>
> I have had this unit in standby now for at least 24 hrs and the pump
current
> when I first switched it lowered to .4 and .2, even an 0.0 for a
second..but
> pretty much constantly switched between .4 and .2ua..
>
> Now the interesting part when I just looked later this afternoon it is
back
> up to .6 again with an occasional .4
> (in standby)..BUT the Cs oven shows 0.1 volts and will go down to 0.0 for
a
> second or so then back up..
> This is not addressed in the manual(at least I could not find it)should it
> not be 0.0 in standby???..
> when I toggle the menus very fast(they are next to each other) this .1
volt
> rise seems to change when the ion pump goes to .6...which it is now almost
> all the time..(unit still in standby..)
>
> Bad news..I just switched the unit into operate and watched all values
very
> closely..when the Cs. voltage started to drop during warm up, started out
> cold at 20.8 and when the oven kicked in,about 13 or so volts, the status
> said raising emult voltage(it has always said lowering it in the past) I
sat
> there and waited and (BEEP)..Fatal error ...see log..
> so I checked the log and got a error (low Cs signal 3 with max emult)..now
> the emult is at 2553.. am powering unit down now to try to restart..
>
> ----- Original Message ----- 
> From: "Dave Carlson" <dgcarlson at sbcglobal.net>
> To: "David Welch" <aceamusements at mchsi.com>
> Sent: Saturday, February 09, 2008 2:41 PM
> Subject: Re: [time-nuts] cs beam tube failure???
>
>
> > David,
> >
> > "when I called them they said these were no longer under factory
warranty
> > because Agilent only offered a 3 yr warranty..and this was one of the
very
> > last Agilent units made.."
> >
> > Not true. In any case Agilent no longer owns the warranty since the
entire
> > business and all obligations were sold to Symmetricom in July 2005.
> >
> > At the time of the divestiture the 5071A chassis had a standard 1-year
> > factory warranty and the High-Performance CBT had a 5-year factory
> warranty.
> >
> > Anyone at Agilent should not be giving out warranty information because
> they
> > do not have the legal right to make those statements any longer.
> Symmetricom
> > owns the rights along with any obligations.
> >
> > As to the Ion Pump current dropping to .4 and .2 uA during standby, that
> > makes sense. In standby the Cs oven is off and the additional Cs
floating
> > through the CBT adds to the load on the pump.
> >
> > It's good that you do see some change in the Ion Pump current. That
means
> > it's functioning properly and that the .6 uA is not an artifact of the
> > electronics.
> >
> > Dave
> >
> > ----- Original Message ----- 
> > From: "David Welch" <aceamusements at mchsi.com>
> > To: "Dave Carlson" <dgcarlson at sbcglobal.net>; "Discussion of precise
time
> > and frequency measurement" <time-nuts at febo.com>
> > Sent: Saturday, February 09, 2008 9:26 AM
> > Subject: Re: [time-nuts] cs beam tube failure???
> >
> >
> > I opened the box for the first time,,the unit was new and still in the
vac
> > bag..the ion current started out and has remained at .6ua..always locks
in
> > about 15-18-min..one other unit he had for sale that the seller had
opened
> > and had running had a (for two days)had a emult of 1715 and also .6 ua
> > current..when I got there to pick up my unit his emult had also dropped
> from
> > 1715 to 1700 in 24 hrs time..
> >
> > one note when I power down or put my unit into standby the pump current
> will
> > go down to .4 and even .2 but not for long ,,,after running for several
> days
> > it usually goes back up to .6..I just had it in standby last night for a
> few
> > minutes and it is still at .4 ua today.but now shows 1295 emult volts...
> >
> > the unit locked for its first time after 2+ years in storage in 21
> > minutes...the calibration certificate shows a manuf date of may
> 11,2005..but
> > when I called them they said these were no longer under factory warranty
> > because agilent only offered a 3 yr warranty..and this was one of the
very
> > last agilent units made..
> > ----- Original Message ----- 
> > From: "Dave Carlson" <dgcarlson at sbcglobal.net>
> > To: "Discussion of precise time and frequency measurement"
> > <time-nuts at febo.com>
> > Sent: Saturday, February 09, 2008 1:47 AM
> > Subject: Re: [time-nuts] cs beam tube failure???
> >
> >
> > > David,
> > >
> > > > I had a similar concern about a brand new 5071a I just
purchased,This
> > unit
> > > is dated may of 05 and was first powered up Jan 2 of this year..
> > >
> > > If it's really been turned off all that time, I'm surprised that it
was
> > able
> > > to power up. Was the Ion Pump current much higher for some period of
> time
> > > before it came down to 6 uA? How do you know it was manufactures in
May
> > > 2005?
> > >
> > > > the ion pump has remained constant at 6 ua
> > >
> > > This may be as low as it's going to get. You might try putting the
5071A
> > in
> > > standby mode for 24 hours or so, to allow just the Ion Pump and not
the
> Cs
> > > Oven to operate. It might bring down the internal gassing a bit. But
> then
> > > again that may be as low as you get. It's not abnormal, especially for
> > older
> > > CBT, or one that has been allowed to accumulate internal vapor
pressure.
> > >
> > > > but I the electron mult volt has been dropping about 1-2 volts per
day
> > > > since then.it started out at 1525 and is now at 1297 and still
falling
> > >
> > > This is fine, and well within expected operation. The 5071A
> automatically
> > > adjusts the EMult voltage to maintain the 100 nA beam current. You
have
> > > plenty of room to drop without concern. The good thing is that the
lower
> > you
> > > go, the more headroom you'll have when ultimately the beam current
> begins
> > to
> > > weaken and need increasing EMult to maintain. It should eventually
> flatten
> > > out before it starts to rise. If it does get down to 800 to 600 volts
> > > without flattening out, then it will very likely have a problem. It
may
> be
> > a
> > > symptom of lots of internal gassing that is getting too much
background
> > > signal to the EMult dynode. No cure for that but to send it in for
> repair.
> > >
> > > > all the other parameters are fine but I noticed the osc freq control
> has
> > > > been dropping also it is now at
> > >  -6.84,started out at -5.50..
> > >
> > > This is fine. You don't have to worry until and if it gets to 50% or
> more.
> > > Then it's time to tune it in, which is a bit tricky. Get copies of the
> O&P
> > > and Service manuals from the Symmetricom web site in PDF format and
> you'll
> > > have many of these answers.
> > >
> > > > do you think these is a problem with this tube?it is a high
> > > perf..should still be under warranty as the manual says there is a 5
> year
> > > warranty on tubes 4240 prefix..
> > >
> > > You appear to have purchased a good 5071A. Did you buy it used? One
> > obvious
> > > question is: Is it locked?
> > >
> > > Dave
> > >
> > > _______________________________________________
> > >
> > > ----- Original Message ----- 
> > > From: "David Welch" <aceamusements at mchsi.com>
> > > To: "Discussion of precise time and frequency measurement"
> > > <time-nuts at febo.com>
> > > Sent: Friday, February 08, 2008 9:59 AM
> > > Subject: [time-nuts] cs beam tube failure???
> > >
> > >
> > > Dave,
> > > I had a similar concern about a brand new 5071a I just purchased,This
> unit
> > > is dated may of 05 and was first powered up Jan 2 of this year..the
ion
> > pump
> > > has remained constant at 6 ua but I the electron mult volt has been
> > dropping
> > > about 1-2 volts per day since then.it started out at 1525 and is now
at
> > 1297
> > > and still falling all the other parameters are fine but I noticed the
> osc
> > > freq control has been dropping also it is now at -6.84,started out
> > > at -5.50..do you think these is a problem with this tube?it is a high
> > > perf..should still be under warranty as the manual says there is a 5
> year
> > > warranty on tubes 4240 prefix..
> > > have you ever run into this before?any suggestions..Thanks David
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