Cleaning of 5970 source

[osp001]

Yes, I know it's an antique, but I'd like to get it up and running again.

I have a .pdf of the maintenance manual, but the images are miserable. Anyone have some better images of the pertinent section for removal, disassembly, and cleaning of the source? I can't identify the parts from the manual, particularly once I get down to the filament assembly level.

Barring that, anyone willing to help if I post some images?

Thanks!

[James_Ball]

Yes, I know it's an antique, but I'd like to get it up and running again.

I have a .pdf of the maintenance manual, but the images are miserable. Anyone have some better images of the pertinent section for removal, disassembly, and cleaning of the source? I can't identify the parts from the manual, particularly once I get down to the filament assembly level.

Barring that, anyone willing to help if I post some images?

Thanks!

Someone threw out my old 5970 manual or I would make copies for you. Cleaning those sources is almost as much art as it is science but not impossible. It has been about 15 years since I did one, but I might be able to help if you post some images. Just watch out for the Eclips that hold the stack together, they tend to fly across the room when you remove them and can do it again when you try to put them back on. The other thing to watch out for is the legs on the ceramic castle looking piece that fits around the repeller as they can break off. I had so complete source around here at one time but I am not sure where it is now after we moved to our new building 10 years ago.

[osp001]

All right- bit of a question: the image from the maintenance manual:



depicts two of number 1, which is described as being an "insulator." I can find only one of these- located on the stem of #10, the draw out lens. Any idea where I might find the second of these, or perhaps it is missing entirely...?

I have an exploded diagram of the source, but nothing on it is labeled. I get the impression they are the part labeled #4 in this diagram:



There are some differences between the items in that diagram and the 5970 I am working on, but they are close.

Lastly, I think the electron multiplier may be the problem, and not the cleanliness of the source. There's a cleaning protocol in the maintenance manual that involves sonication in trichloroethylene- not an option. Now, the source in the 5970 I have is one of the round ones, not the rectangular ones; is there any reason it cannot be ultrasonicated in methanol for cleaning? I know it'll probably have to be replaced, but what's the worst I can do- ruin a part I'm already going to throw out? Perhaps acetone would be a better choice...?

[James_Ball]

The lower image is the source from a 5995/5996, which is evident by the long probe that attaches to the top or bottom as they were installed with the source down in the analyzer.

Part #4 in the second image should be the same as part #1 in the first image and those are the repeller insulators.

Part # 19 in second image is the same as part #11 in the first image and should be a white ceramic insulator that fits snugly around the drawout lens.

Image two should be the best to follow as it is accurate in the way the pieces fit together. The difference is that part #6 in the first image replaces parts 1,2 and 3 in the second image. It is the last part you will put on and the first you take off. It is what guides the column into the repeller. You put the brown vespel insulator #4 onto the repeller #17 and slide that up through #16.

Screw #10 and washer #11 hold the filament block #14(Assembly #5) to #16 which is held to #24 by screw #15 and washer #11.

Part #5 from image one will slide into the filament block and then you drop the second vespel insulator #4 on the repeller #17 and screw #6 from image one onto the repeller to hold it into place. Parts 18,19,and 20 fit into #24 and are held in place by #27.

I have probably totally confused you now lol. What you have is the lower lens stack which is #27 and below held to the bottom of #24 with the ceramic pins and all those C-clips and washers, and be sure you look carefully at those when taking it apart so you can get them all back together correctly. The clips are a major pain in the backside. Once those are together then the above assembly drops in and screws on and you can then screw that into the magnet ring #21.

#18 is the ion chamber, and the filaments have to line up with the slots in the sides of the cylinder. If you have the block which is #3 in the first image, you mount and assemble the filament assembly to that and you will notice that there are openings in the block that line up with the filament wires. You use those to gently align the filaments, once the filaments are aligned with the openings they will line up correctly with the slots in the ion chamber once everything is assembled.

If you have any other questions just ask. It is much easier to teach someone to assemble one of these in person, but I will try to help as much as possible.

[osp001]

Whew- everything cleaned (I hope) and reassembled. I tried autotune right quick, and after some messy tunes, I got and for the first time ever, but that quickly passed. Instead, I got "cannot achieve constant peak widths."

I know there's liquid BSTFA in the sample holder.

Would cleaning the electron multiplier do any good? It's a little odd in that it's one of the round plug-in style EMs, not the rectangular-ish ones that prevailed in the early 5970s. The manufacturer says the EM can be cleaned with ultrasonication in IPA, then dried at 80C. Or would that just be a waste of time because it just flat-out needs replaced?

[James_Ball]

If it is BSTFA in the vial? I know the ones I used always tuned using PFTBA looking at mass 69, 219 and 502.

The original EM was the Galileo tube type, but there were upgrades to either the round K&N horn or the foil ETP multipliers. If you have the round horn it would be best to just replace it. If you have trouble finding the right one give Scientific Instrument Service a call they usually carry them.

If you open the valve and do a manual tune can you see any peaks at all?

[osp001]

Sorry- long day of derivatization. Yes, it should be PFTBA in the vial (I have no reason to believe it is something else, anyway).

Valve open and manual tune attempt:

Mainly got messes like before; the next two images were exceptions.





Then I got this:



The "excessive signal level" appears to be caused by too high an output from the detector. A defective detector, perhaps?

Maybe it would help to run the vacuum overnight, as the instrument has been off for a considerable period of time.

[James_Ball]

I always had my best luck after pumping down over night, giving the temperatures time to equilibrate since the source isn't directly heated, but is heated by the transfer interface.

Always leave it under vacuum and heated, it will keep it clean and ready to use and doesn't take that much electricity.

If the multiplier has been sitting at atmospheric pressure for an extended period of time it probably needs to be replaced. All day won't hurt while you are cleaning, but weeks and months can.

When you install an new one, let it pump down for at least a few hours, over night is better, before you put any power to the EM. Set it to 1000 -1200 volts and save that tune as ATUNE before starting the autotune process. From there if everything else is good it should be able to tune itself, if not, use the " reset to defaults " option in the tune menu, it will take longer to tune but it may need to be reset if the parameters are too far out of normal.

[osp001]

Just as an update- I kept it under vacuum and heated overnight, and tried both manual and autotune. I got some clean-ish peaks in the 60 AMU region, and the tune shut down automatically. Error message was "There is not enough signal to begin the tune." Looks like a lot of potential causes for that- including a bad detector. Didn't seem to get any peaks at 69, though. Happened too fast to get a screen cap.