I’m hoping someone can help me with a problem that has developed on my
MAT252. I recently went through a flurry of bad refurbished filaments (no
trap emission) and now that I have a nice new filament in there, I can’t get
the source, or pumps, to stay on more than a couple minutes after turning
the voltage up to the full 10 KV. I haven’t yet opened the ConFlo, so it is
in dual inlet mode. I left it overnight with the HV at 8 KV, and the pumps
were still going this morning, but the HV was off (source control still on).
HV reset OK. Vacuum was at 3.6 E-9. Within 2 minutes of turning on the HV to
10 KV, the pumps tripped again. I’m lucky now in that after half a dozen
trips over the last three days, I’ve at least figured out how to reset the
pumps before they vent so that I don’t lose vacuum. As long as I am in the
room.
I’ve had a similar problem to this in the past, and the problem was with a
couple capacitors the vacuum gauge monitor, which was giving faulty signals
causing the trips. At that time, the needle valve on the analogue vacuum
display had been “jittery” and then outright failed. And the inlet
forevacuum display in Isodat had been jumping around. But I haven’t seen the
same symptoms this time, except perhaps that the vacuum during CF mode
seemed slightly lower than normal (2.6 E-6 as opposed to 4 E-6). I note that
the vacuum gauge display is not responding at all when the pumps trip, until
I can reset the MS, restart Isodat system, and toggle the vacuum display
buttons. Toggling the buttons is a trick that has always been necessary from
time to time to get the analogue display to respond. Until the analogue
vacuum gauge display returns to an active reading mode, the pumps will not
restart. As with my earlier problems, this suggests a possible problem with
the vacuum gauge monitor again. However, I don’t recall there being a link
before to having this happen only with HV at the full 10KV.
And here is another piece to the puzzle… I just decided to keep an eye on
the source forevacuum (through the analogue display since I can’t figure out
how to get it to display through Isodat) to see if it was displaying any odd
behaviour. Since I have switched it to this setting, still at 10 KV, it
hasn’t tripped yet. As I write this it’s only been 1 ½ hours, but it hasn’t
tripped yet. I couldn’t get more than 2 minutes of run time this morning and
yesterday when set at 10KV while monitoring source high vacuum.
Does anyone out there recognize these symptoms? At this point I’m still
thinking it is the vacuum gauge monitor. I should know by the end of the day
whether this is directly related to the analogue display being set to the
source high vacuum at 10 KV only, or whether it is a fluke that it hasn’t
tripped again.
Thanks for any insight.
--Alison
_____
Alison Pye • [log in to unmask]
Stable Isotope Lab Coordinator
CREAIT • TERRA Facility • Stable Isotope Lab
<http://www.mun.ca/creait/TERRA/SIL.php>
Alexander Murray Building
Memorial University of Newfoundland
St. John's, NL • Canada • A1B 3X5
ph: (709) 737-3217 • fax: (709) 737-2589
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