[time-nuts] Thoughts on Cs tube failure modes

aceamusements at mchsi.com aceamusements at mchsi.com
Tue Dec 2 14:15:34 UTC 2008


hi,

I sent u a few emails back about a year ago when I purchased my brand new 5071a
and had a strange continuous drop in the emult voltage since power up(on jan 2
of this year)about 1-2 volts per day,I later found out this was normal with a
new tube and it should level off and then start to rise before it dies 5-6 years
form now

 so far the emult has stabilized at 1203v and has not started to rise after a
slow fall(over 6 months,started when new at over 1550v).


what I have also noticed though is the ion pump has risen slowly in this period
from .2UA to 4.8UA  slowly over time,I have tried both unplugging the unit for a
few days and restarting it in standby which lowers it a small amount (to about
3.2 but when I turn the unit on into operate it just goes back up to about 4.5
to 5.5ua..Is this normal or possibly a contaminated tube?I still have two years
warranty on the tube,but this unit was sitting in storage over 3 years since I
purchased it new and unopened carton..(one interesting note the pump current
which I have checked every few days has very slowly risen since power on 11
months ago and even after reset will always go back up to about 5Ua (even though
this tube never, when new, was over .6ua in standby( usually.2ua operate
.6ua?)any ideas why this would occur?

Other than the rise in pump current the unit has worked fine since unpacking out
of the box..Thanks David..



----------------------  Original Message:  ---------------------
From:    Corby Dawson <cdelect at juno.com>
To:      time-nuts at febo.com
Cc:      time-nuts at febo.com
Subject: Re: [time-nuts] Thoughts on Cs tube failure modes
Date:    Sun, 30 Nov 2008 18:35:27 +0000

> John,
> 
> What you describe with the ion pump curent is normal if the tube has been
> powerd off for a long time.
> 
> Th mainframe normally would turn the oven and ionizer filaments off when
> the ion pump current pegged.
> 
> After minutes (can be quite a few minutes) the ion pump current will drop
> as it pumps the surge of outgassing from the heated filaments.
> 
> The cycle repeats and can take a couple days on a stubborn tube.
> 
> You bypassed that circuit so I'm not sure how much gas you introduced.
> 
> If after a couple days the current is still pegged try connecting an
> external high voltage supply of around +3000VDC that can provide at least
> 5ma. (turn unit off)
> 
> Let it run overnight and if the current comes down reconnect the internal
> power supply and turn the mainframe back on.
> 
> You probably will see it peg again and the see the oven shut down (it
> happens fast!), just leave it on and it should start cycling and
> eventually the filaments will reach the oven set points and have
> outgassed enough so that the protective circuit will not trip.
> 
> Then you can try to see if the rest of the tube has any life. (you may
> have to reduce the oven set resistor to 130 ohms as well as reducing its
> companion overtemp resistor. This is the value the Navy uses to get the
> last bit of life out of the tube, don't do it if you can get the rated
> beam current at the original value!)
> 
> If you email me I can give you my evening phone number if you need some
> more info.
> 
> Corby Dawson
> cdelect at juno.com
> 
> 
> 
> 
>  
> ____________________________________________________________
> Click here to find the perfect picture with our powerful photo search features.
> http://thirdpartyoffers.juno.com/TGL2141/fc/PnY6rw1aBm8XXBA9eC72NBG9alhmVMe3ZD9u
> ri8B4mlt3xxDXctvb/
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list