Dear all,
Many, many thanks to all the many respondees for taking the time and making the effort to respond. Hope it is ok I don’t list people.
The joke in the lab when the problem happened was “Ahhh, just hit it with some WD40,* that’ll do the trick!”
* Other lubricant brands are available.
Well, as it turned out, that actually was the most common suggestion!
I could actually move the slider one or two spots occasionally when the probe was out with some jiggling (side-to-side, pulling it out a bit), so maybe it was not so badly stuck in my case. I squirted some WD40 – as little as I could and mopping up the excess – into the hole for the moving tool of the offending slider whilst jamming some plastic at the end to lift the slider up and then let the probe hang upside down for several hours so the lubricant could make its way down to the ball. After that it was absolutely fine and moved freely. Too easy.
Here is a summary/listing (repeats left off to keep things limited) of the responses. In short though, it was either try your luck and apply some lubricant (WD40, Q20, Never Seize, fine oil, contact cleaner, silicone oil/spray) or open the slider unit up and clean, perhaps apply lubricant, or change the ball if it is too broken or too worn. What to open up and how depends on the probe design and what is actually stuck, for my probe it seems it should be possible to open the slider unit without taking off the probe sleeve, but in my case I did not have to open up anything.
Selected responses (edited to make it clearer to read):
We put a little silicone spray on to the probe and let it to soak in, then jiggled it.
Where the sliders are located, it is possible to open the slider unit. I guess that the glass ball is no longer as round anymore as it should be.
Try taking the slider mechanism off and clean it. WD40 helps.
There are small glass balls in there that act as bearings...they may become stiff over years of use and need to be reseated (to buy a bit more time) or replaced for a better fix.
You can try to apply just a little pressure side-to-side while you also apply some force to move the slider from 9 to 8 (etc.). If that doesn't get you anywhere, you could try removing the probe to see if you have any better luck moving the slider while the probe is on the bench.
If you can take the probe out hold it upside down using a lab clamp of some sort to keep it there and spray a little fine oil, say Q20 or whatever you can find locally in hardware shops and just leave it a good few hours, say overnight. The oil will slowly work it's way down the tuning rod and in time (this is the key) it should loosen. Do not apply too much oil as very little is actually required and you do not want the oil all over the probe either as it may one day migrate to some part it should not migrate too like the RF insert so use a little feeling as to how much. Should you ever sense a background on the RF insert this too can be cleaned by immersing just the top RF insert section of the probe in isopropanol for a few hours and then letting it dry out with a little VT gas before putting it back in the magnet.
The difficulty to move is coming from the gold plated sliders with numbers at the bottom of the probe hooked up to the green rods. You could use mystery oil in a syringe, squirt a tiny bit into the opposite side with the numbers. The issue is not in the electronics but down where the gold sliders are. There is a small glass bearing there that can get stuck, usually lubricating it will free it up. If you can move the sliders up to the zero position and then look on the back side of where the numbers are there are small indents and if you use grease applying just a small amount and work the slider up and down. It should free up.
I have used a lubricant with limited success. These sliders ,except for the continuous one at the right side have small metal balls in them along with a Teflon washer, unfortunately the only way to fix them is to take the sleeve off the probe, the screws off the fiberglass rods and the 2 screws at the bottom of it - then the board should be free from the probe. You'll have to remove some screws from the plate and now over white paper remove the plate - don't loose the balls they are small. The ball should fit in the small hole. I also used Loctite on the 2 screws holding the board on, it helped.
For Bruker probes with the sliding rods for tuning and matching, the opening showing the numbers which are selected are held in place by a number of small screws, typically either four or six. These selection rods usually have small indentation drilled into the back side of the slide, i.e., opposite side from the numerals that a displayed. The rod then slides over a small glass ball held in a single indentation on holder, i.e., the ball itself does not move from this hole. The repair itself is simple.....at least to describe. However, dealing with the small glass ball and not losing any parts can be challenging. In short, you remove the small screws holding the plate over the numbers. Typically the probe should be horizontal of a flat surface so that the small balls for each of the slides are not accidentally lost. Gently lift the rod which is stuck. The ball need not necessarily be removed (but it can be to make certain that it is not broken or dirty). A little bit of silicon grease, the kind of grease that Bruker used to provide for variable temperature connections works well, should allow the ball to once again freely roll in the indentation. Lower the rod back in place over the ball and replace the screws. Having done this several times myself, all this is generally much easier to say than do. The glass balls can stick to unwanted surfaces and can also pop out to be easily lost. On the other hand, once you have opened it and seen how the device works, it is actually a very simple design. While opened, I suggest cleaning and adding grease to all the slides that have the balls. Usually the last slide is continuously variable and, as such, does not have one of these glass balls.
I have used a spray bottle with MeOH to get the gunk out of the slider, then follow with heating it with a hair dryer once the MeOH has evaporated. I but a dab of never seize on almost all sliding and threaded parts of probes. There are a few dissimilar metals that don't do well with continuous contact and then there is always Galling with thread components with differing hardness. To verify you can check with Bruker on how to clean a cryo probe, upside down flush with MeOH. I have dipped entire probes bodies into a large graduated cylinder of MeOH, works well.
Take out the probe and unscrew and remove the slider frame. Keep the probe horizontal and take off the sliders. You will see three sets of small bearings. The set of the slider that is stuck will be messed up. Put it in order and re-assemble the construction. You'll be fine. I did it here several times with my old probes.
There are tiny balls behind each of the tuning and matching sliding sliders. I would try to spray some 'electronic contact cleaner' to the back of the sliders first. This might free/remove the dirt. If this still doesn't fix the problem, you can try to apply some low viscosity synthetic lightweight oil to the back of the slider. It might work better than the cleaner spray. I did try to remove the sliders once on an old BBO probe years back. I ended up lost one of the tiny balls.
Difficult to say without having a look at it - possibly one of the internal capacitors (which are normally soldered in) got dislodged and is stuck. You’d need to open the probe and inspect the capacitor slider.
We once had such an issue with or BBO probe, a little bit of silicone spray has helped, but not too much!! Maybe you need to cover the remaining parts of the head with paper tissues. Gentle warming with a blow dryer after the treatment can also help.
Take the cover off the probe and lubricate the capacitor mechanism with a small amount of contact cleaner.
Regards,
K. Klika
Received on Wed Nov 06 2019 - 03:40:16 MST