AMMRLers,
I apologize for the delinquency of this summary but better late than never
I hope. I think it's important to get all of this information into the
archives.
First I'll provide a summary (starting upstream and working my way down
towards the probe) of the suggestions and what eventually seemed to work.
Then, at the bottom, I've pasted the contents of each reply.
1) Check your air (or N2) pressure.
2) Clean the upper barrel. We use a wooden yard stick with several layers
of Kim-Wipe taped on and moistened with EtOH. Be sure to hold the barrel in
place as you remove the stick.
3) Adjust the position of the upper barrel and/or the probe with respect to
each other.
4) Remove the stack and refurbish/replace as necessary: a) the tubing, and
b) O-rings. Also, clean out the airways with a combination of solvent and
clean, dry, high-pressure air (applied from both the upstream and downstream
directions). One might also consider wrapping the threads of the nipples to
which the tubing attaches with Teflon tape for a better seal, and securing
the tubing to the nipples with plastic tie-wraps or a wire tie. Also make
sure all the fittings both inside and out are securely screwed in.
5) Wipe the spinner and NMR well with EtOH or IPA before each use.
6) Try a different spinner, they wear out.
7) Make sure that the spinner is in fact not spinning and it's not just a
problem with spin detection due to: a) a broken spin sensor, b) the white
or reflective dots on the spinner, or c) the height at which the spinner is
floating.
8) Check the spin-rate solenoid for lodged dust/dirt and/or wear on the
bushings.
9) Adjust the thumb screw (just above the yellow solenoid) which regulates
the spinner air pressure.
10) Try adjusting the amounts of VT air and Probe cooling air going into the
probe. They all share a common source so adjusting one effects the others.
11) A cracked coil insert which is affecting spinning (look for scoring on
the NMR tubes).
I believe it was a thorough cleaning of the barrel air lines as described
in 4) above that eventually did it for us. It didn't work the first time
though, and I think it required pushing solvent and air through in both
directions, that finally dislodged whatever was in there.
Here are all the replies, in the order they were received:
>
> Are you sure that the probe is OK? A cracked coil insert (speaking from
> all too recent experience) can cause intermittent spinning
> problems..before it falls apart altogether.
> If this were the case, you might see evidence of scoring on sample tubes.
> I would recommend pulling and inspecting the probe carefully.
> I don't know how spinning is regulated on the Unity, but the spin-rate
> control solenoid on our INOVA system needs periodic replacement.
> Michael Strain
>
>
> John, I don't know the Varian system but have you looked into the
> possability that due to the filter maintenance, the spinner air control
> valve may have gotten some dirt knocked loose into a very tiny orifice
that
> might be causing your problem?
> Bob Silverman
>
>
> Have you looked at spectra themselves to make sure you aren't spinning (no
> spinning sidebands). I once had a problem with the 500 that appeared to
be
> dirt, etc., at first, but found that the led sensor unit had gone out.
> Also, if you have older spinners (with spots, instead of alternating
> black/white tape, you might try repainting the spots. A third possibility
> is to try some different spinners. We've had some that just seemed to
wear
> out after long use.Best Regards,
> Ron Nieman
>
>
> Hi John,
> I'm not sure I'm going to be much help to you because it sounds like
you've
> tried everything, but for what it's worth - I recently had a similar
> problem with our little gemini. Our problem seemed to stem from students
> frequently forgetting to thoroughly wash their hands after wearing>
> powder-filled examination gloves in the lab (horrible pervasive stuff
> that). Regardless of the cause, our symptoms were very similar to those
> described above, i.e. irregular spinning problems over several weeks,
> despite normal cleaning efforts etc. We appear to have solved our problem
> (touch wood) by "getting tough" with the stack, i.e. we disconnected the
> solder, unscrewed the fitting, and then did a number of cycles of swabbing
> the bearing vents with a good dose of i-PrOH and then attaching high
> pressure air to the connectors to really purge the vents. That was about
> eight weeks ago and the spinning has been fine ever since. Not sure I
> recommend shock tactics at regular intervals, but at the time I was
feeling
> frustrated enough to cross-the-line.
> I hope for your sake the problem just goes away and leaves you alone.
> Dr Sue Boyd
>
>
> John,
> Most of our spinner problems are "fixed" by washing the spinner
> with soap and distilled water. Rinse well. I *think* that oil
> from fingers on the bearing surface causes the problem. A good
> preventive is to wipe the spinner with a kim-wipe every time
> you put a sample in the magnet.
> dave scott
>
>
> John, I can't really think of what else you could do. Just one
suggestion
> you may have overlooked: clean the spinners.
> Michael A. Bernstein
>
>
> Dear John,
> Last year we had a similar problem with the eject air on our INova
> 500 and just recently on our Mercury 400. It seemed the amount of
> air was different every time we ejected. Since we have a dry scroll
> compressor with an air dryer I new it wasn't the air it self. Some
> tubes would eject, but others wouldn't, or so it seemed. Turning up
> the air pressure only made things worse. It turns out that on the
> upper barrel assembly, on the inside, the air hoses coil around the
> barrel starting from the top and going to the bottom. The eject air
> tubing is a larger diameter than the spinning or bearing air. Though
> they had secured it at the top with a Tie wrap (wire tie) they hadn't
> at the bottom, So we did on both units. Your problem sounds very similar.
> You may want to check the air connections on the inside of the barrel.
> Also the hose can get crimped very easily when the stack is being put
> back in. Make sure they all run parallel to each other and don't cross.
> I have also found on both our stacks that the fittings on top were loose
> and required tightening with a screw driver. I hope some of this is
> helpful.
> John Wilderman
>
> John:
> Varian spin systems are extremely fussy ... as opposed to bruker.
> I'm assuming that the spinner is not hovering too high so that the white dot
> is above the detection range of the sensor. To check that ... turn the air
> off and lsten to here if it falls...wait a good minute for air to bleed out.
> Turn the air back on and if it spins now then that was the problem.
> If you have an auto-matic spin controller you can press the reset button on
> it sometimes to get control. All I know is that there is a fine balance
> between slow drop air, system air and VT air and you should record the
> values of these settings when it is running well. Also there have been many
> bugs and VNMR patches with these boards.
> Even with the automatic spin controller boards the spinner can be in several
> states of control either not spinning at all ... (no green light), spinning
> but not regulated (green light flashing), spinning and regulated (green
> light on steady). There is one very scary state that it could be in ...
> runaway out of control spinning where it could be spinning as high as 100Hz
> with or without lights or speed indicator. An eject at this time will break
> the sample more times than not.
> If you beleve that it is bore contamination that is causing your problems
> then it may be time to get tough on protocols. This is what we do in
> Chemistry at UF:>
> Be very careful to mark the position of the upper barrel. There is a lot of
> play and in some magnets this will cause tube and insert damage=probe
> repairs. I run a magic marker arround the screw notches of the top bracket.
> Clean the upper barrels 1/week with what amounts to a giant Q-tip swab.
> Clean spinners inside and out 1/week.
> Dissasemble and clean the inner workings of the upper barrel 1/month ...
> including the tiny inner orrifices. These can get momemntarily blocked by
> loose particles that later fall away and subsequently reblock.
> Every sample needs to be cleaned with a kimwipe and the spinner cleaned each
> time it is used. At no time should a spinner be touched with bare fingers.
> Hold it with the kim-wipe when inserting.
> Violators are spanked with wet noodles, there accounts are canceled and
> there desk is set out in the parking lot next to the dumpster.
> Even with these strict protocols you should see the junk that comes off a
> clean kim-wipe run through the upper barrel!
> When all else fails ... blame the users and up the charges:)
> Robert Harker
>
> John:
> What a pain!!! I know how you feel!! There is a thumb screw above the
> bearing solenoid.....did you try adjusting that? Just start by turning
> it a 1/4 turn or so.......I'm assuming that you replaced the solenoid
> (the yellow mechanism)..How old is your magnet?....I had to replace my
> upper barrel assembly......Please let us know how you make out. Good
> luck.
> Janine N. Brouillette
>
>
> Dear John,
> It seems like you checked most everything.
> We have a VXR. A dirty upper barrell or turbine have been the causes of
> most of our problems. You need to take the barrell completely apart to
> clean it. You may even want to flush out the drillings with alcohol,
> and if there are no plastic parts, xylene.
> You also my want to check the computer controlled valve that regulates
> the air flow to the spinner. You can probably find a repalcement at an
> industrial supply outfit.
> Gary J.
>
>
> Hi John;
> I would try the followings.
> Put a sample tube not all the way to the proper depth but just barely
> appearing from the bottom of the spinner. Inset the spinner. If this
> spins well then problem is not likely in the "upper barrel" -- air
> bearing etc. Push a sample tube a little and see if it spins properly.
> If it fails at some depth then problem looks to me a sample tube is
> touching inner wall of the insert (or the top of probe), provided the
> sample tube is fairly straight (and spinner is clean). If you have
> another spinner or two you can test if all behave the same manner.
> Toshi Nishida
>
> Hi John,
> If I were you...... I would be very tempted now to change the bearing
> surface. Easier said than done of course, however, I seem to recall you
> mentioning you had a few spectrometers in your lab. If you were to have a
> look at just the bearing assembly part of the upper barrel, you should find
> it to be identical for all spectrometers from 200-400, even WB systems. The
> other differences between the various magnets is just the length of the
> barrel itself. This implies you can exchange a 200 base part of the upper
> barrel with your 400. If the bearing surface is indeed the guilty part the
> problem should now appear on the 200. If so, viola, you now know exactly
> what's casing the problem, and can narrow thing down dramatically.
> If the problem stays on the 400..... there are several other tricks you can
> try to narrow it down some more: A few are:
> 1) Either raise the sample tube or lower the probe and try spinning again.
> This gets rid of the possibility of the tube touching something in the
> probe.
> 2) The best way to adjust the centering of the upper stack is a fair
> question, however, you only have a few mm play in the X-Y plane. I normally
> set the spinning speed up to some high value that it could never reach,
and>
> adjust for the highest speed. (Minimum resistance) Another way is to set the
> speed to say 5 Hz, set up the probe for inner coil tuning (X on a BB probe,
> H on an ID) and set the tuning meter to mid scale where you can easily see
> the perturbations from a sample slowly spinning in the upper barrel. A
> sample that is not perfectly in the middle of the coil will have higher
> deviations on the tune meter than one that is perfectly round, and centered.
> Once again, adjust the upper barrel so the deflections from the slowly
> rotating sample are at a minimum. (Not so easy to do if you cannot see the
> tune meter from the top of a high magnet, but a colleague can tell you if
> it's 'better or worse now')
> 3) Make sure the probe is centered and snug against the upper barrel. To do
> this put a small mark with a pencil or whatever on both the current probe
> position and upper barrel height protruding out of the magnet at both ends.
> Then slightly loosen the probe flange to the point where you can push the
> probe up until a colleague informs you the upper barrel also moved up. Then
> have your colleague push down on the upper barrel until it meets up against
> the top of the RT shim coils. Tighten the probe flange. If you find a
> difference in the marks not only have you found out why the pneumatic seal
> was not working too well (this causes eject problems, not really spinning
> problems) but you will need to re-shim your probe. Even a single mm makes a
> dramatic difference to both variables.
> There are many more tricks, however, I suspect this should be enough for you
> to get on with for the time being.
> Once your machine works fine again..... I would love to know just how well
> (or badly) my new spinner works at low temperatures!!!
> David H. Cross
>
>
> John,
> We had problems with our Varian Unity 400, but it was our fault.
> Researchers had spilled a sugar solution, clogged the orifices, and
> neglected to let me know until there was no spinning. That was easy to
> correct after pulling the upper barrel and washing with first with water
and
> then EtOH, with and without the air flowing through the orifices.
> The problem you describe is almost exactly what we had experienced with
> Varian's Gemini 200. We think the main problem is due to users putting
> their fingers on the spinner spots but have had to remove and clean the
> upper barrel. Using a flashlight to search for any barrel dirt.
> Hope you have lots of additional suggestions,
> Keith Burke
>
>
> John:
> We have Bruker equipment here, so I don't have
> experience with your system. I've found that the
> plastic spinners wear out and eventually won't
> spin. Have you tried a new spinner? If yes, then
> never mind. Good luck.
> Jim
>
>
> John,
> Check the solenoid metering valve in the magnet leg. This thing has
> a little stainless steel diaphragm that is prone to breakage. The part
> is a Clippard model EV-242 and they are MUCH cheaper when purchased
> through a valve supplier (rather than from Varian). We don't use the
> spinner much any more, but when we did, this beast broke at roughly three
> year intervals. The valve is located at the lower left corner of the
> magnet leg.
> Bill Kearney
>
> Hello Sir,
> I saw your recent AMMRL Posting about spinning problems.
> My approach to spinning problems is to first thoroughly clean upper barrel.
> I carefully unscrew the tube from the bearing housing.
> Any twist to the wires going to the tachometer optical sensor and PFG
> leads(if equipped') guarantees you will be heating up a soldering iron.
> The solder leads are extremely brittle so be very careful as you unscrew
> the tube.
> I use Kim wipes and solvent with a fiberglass rod to push them through the
> tube. After five or six passes usually the Kim wipes are clean.
> In case of a sample break or extreme amounts of gunk I would use a bottle
> cleaning brush on the tube..
> I carefully inspect the air bearing surface. I have seen several wear out
> over the years. If it is deeply scratched it my be no good. I usually
> avoid CHCl3 to clean this area because of the plastic housing of the
> optical sensor.
> Generally q-tips and ETOH work well here. I clean the bearing surface with
> all the hoses and wires still in place. After this is clean, I carefully
> put the tube back into the top plate and make sure all the hoses are
> properly wrapped. The tube should be hand tightened firmly back into the
> base.
> If this is loose you are guaranteed a lot of intermittent spinning problems.
> If I still have spinning problems I then change out the spin solenoid valve.
> The spring washer inside and the rubber seal will wear out over time.
> This may require re adjustment of the bearing air. I generally turn it off
> all the way and then open it 1/4 turn pass where it first comes back on.
> Also, The amount of VT air going into the probe usually makes a bit of a
> difference to how much bearing air you will use. On Varian 5mm I usually
> set the VT air flow to 10-12 lfm rate.
> Another thing that can cause spinning problems on the UNITY system are:
> If the bottom fan in the CPU card cage is burned out or slow the automation
> card may overheat, causing weird intermittents in spin control.
> Please let me know if this helps, I was a Sr. Field engineer for Varian for
> quite a while and maintain a large amount of NMRs here at Merck.
> Tom Kalisker
>
That's it; thanks again for all the support and information.
Tomaszewski, John
NMR Facility Coordinator
Indiana University
800 E. Kirkwood Ave.
Bloomington, IN 47405-7102
(812) 855-4478
Received on Fri Aug 09 2002 - 11:35:42 MST