5973 "Difficulty in Mass Filter Electronics"

[benhutcherson]

I have mentioned here several times that I'm working on getting a 6890/5973 going at my new place of employment.

As a bit of background, I know this came from a water lab, and is plumbed in such a way as to make me think it was likely on a purge and trap(the He line to the inlet was cut and had fittings installed).

I'm waiting on a source temperature sensor now, but in the brief time I can get it to operate before the temp sensor goes wonky, when I go into manual tune and hit profile the PFTBA valve will click on, I will see the normal profile screen, and after a second or two the valve will click off and it errors out with "Difficulty in mass filter electronics."

I can't do any real troubleshooting until I can solve the temp sensor runaway, but I'm wondering about possible ideas.

I've seen suggestions of anything from a dirty source all the way up to a bad sideboard and several things in-between.

I haven't actually cleaned the source properly yet(I'm trying to track down our US cleaner) but did take it apart and to my eye it "looked" clean(I know that doesn't necessarily tell a ton). The filaments both pass a visual test, and even though I know that's not necessarily a 100% guarantee, although past experience has told me that the error there would be "No Emission current."

The connector on the repeller is bent pretty badly, so one issue I'm wondering about is if a cracked insulator there could cause this problem(haven't had it apart yet to check). The source is on my to-do list hopefully next week.

I've verified connections to the quads and source from the pass-throughs, and they are tight.

I know dipping the coils is a diagnostic step in this, and I will certainly try it once I can keep it going long enough to do that. I'd normally do it out of habit anyway on an unknown instrument, even though I've never actually appreciably changed anything by doing it(although I could see someone messing with them and getting them out of whack attempting to "fix" it without monitoring the voltage).

I've also seen cleaning the quads, but that's a last resort option to me.

Two other things came to mind too. When I first came to this, every easily reachable connection was disconnected. For one thing, the BNC connector(EM?) has some corrosion on the barrel, although the pin and the inside of the barrel are clean. Another is I'm wondering if the HV cable?(the one that looks like a miniature spark plug wire) can/does go bad.

Does anyone have any thoughts? Needless to say, I'm going to rule out every possible thing before attempting a new sideboard. That leads me down a dangerous rabbit hole, since if I'm buying one I'd rather buy the fast scan version, and I seem to recall that fast scan is not compatible with HPIB.

[James_Ball]

Yes, the HED supply connector (spark plug wire) can go bad. I had one where the center pin in the feed through broke and it would give intermittent problems because when it was touching it would work then a little vibration and it wouldn't, then it would work again. Usually it gave a spectrum that looked like grass, a hit on all masses, it can also distort the peaks enough to give the error you listed. The feed through is not expensive and just screws apart with an o-ring seal.

Usually when you get that error it is because tune can't form a proper peak, either the width is far too wide or narrow or it is just finding noise. Reset it to defaults, if that option is in the version of MSDChemstation you are using and try it.

When you see the normal profile screen, are you seeing any peaks? or just the screen with three windows. If you try scan, do you get a mess of peaks all about the same height and almost every mass?

[benhutcherson]

Thanks James.

Unfortunately, it seems that my board has been pronounced dead.

I went in to dip the coils and at 100 I was seeing 4mV. I then set it to 500, and saw the same value.

I called Geoff, who told me that when the voltage goes too high, it "rolls over" and reports an artificially low value. He suggested setting a lower mass range and seeing if I could dip the coils at that to get them in the ballpark, and then work from there.

So, I ended up at 10m/z, with a voltage of ~950mv. I made some pretty serious adjustments, but only managed ~850mv. Geoff pronounced the board dead based on that. I did double check the quad pass-throughs but they were good.