Agilent Mass Spec Error

[briand]

Has anyone seen this in their tune? Agilent GC/MS system mass spec 5975C. It sporadically fixes itself and the normal peaks for PFTBA appear as normal but this is rare. Sometimes tapping on the sideboard randomly makes the peaks appear. Not sure what is happening and the instrument is unusable. PFTBA is open and closed there is no change.

[rb6banjo]

That's just noise. Do you still get peaks in your chromatograms?

Did you try to switch the filament? There are 2 in the instrument so it's a software switch. The box is in the screen shot you provided but I can't see if it's set to 1 or 2.

I'd try to change that and see if you can get it to tune.

If my suggestion works, the next time you burn out a filament you'll have to take it apart and replace them both. I just had one burn out on me and had to change to #2.

[briand]

Hello,
There are no peaks in any known samples during a regular run. This occurs with both filaments. The mass spec data for all runs pops every ion in our range so the spectrum looks like a black rectangle. The manual tune says "no peaks found". I have already accounted for a possible corrupt tune file as well.

[rb6banjo]

Is it possible that both filaments are compromised?

[briand]

Doubtful but thank you.

[rb6banjo]

Seems like it might be a service call. I'm out of suggestions. I had a high energy dynode (HED) fail on me on a 5973N years ago. Similar symptoms as I recall. It's been a while ago.

[briand]

Thank you I will check on that

[James_Ball]

Seems like it might be a service call. I'm out of suggestions. I had a high energy dynode (HED) fail on me on a 5973N years ago. Similar symptoms as I recall. It's been a while ago.

The HED is just a piece of stainless steel, unless the ceramic insulator breaks they should not fail, though they can get contaminated and need cleaning.

What the OP is describing sounds like it could be the HED cable or connector. We had the same problem and the pin in the connector that passes through the side plate had broken off and was in the HED cable(the thick white and red one that looks like a sparkplug wire). If it is the black connector it is easily replaced, it just has a plastic nut on one side and o-rings on it to seal it to the side plate. The wire is also easy to replace, but you have to open the electronics compartment to attach it to the board then run it up and attach to the side plate.

[briand]

Thank you for the insight. I have just replaced this cable as I had thought the issue was due to this. However after replacing the broken cable (broken pin) the same issue remains. Perhaps I will check the HED for signs of failure.

We might have a power supply issue.

[James_Ball]

Thank you for the insight. I have just replaced this cable as I had thought the issue was due to this. However after replacing the broken cable (broken pin) the same issue remains. Perhaps I will check the HED for signs of failure.

We might have a power supply issue.

Does the cable fit correctly? When I first replaced the cable on ours it did not fit completely tight. When looking at it the broken half of the pin was still in place and preventing a complete connection. It is why we had to replace the connector also.

The HED can be removed with two screws and the stainless steel button can be cleaned with isopropylalcohol and a Kemwipe.

[briand]

We have tried that thank you. We will have to call for service.

[aldehyde]

Unfortunately the image is broken so I can't see, but I'd like to add that the HED itself doesn't fail---but the cable can become damaged, the power supply can fail, and the vacuum feed through for the high voltage from the power supply to the detector can leak.

I'm talking about the feed through where the orange white cable connects. You know how that cable has a weird gasket like cover? That's because vacuum actually makes it through that feed through and so the rubber gasket material is used to prevent a leak. If the cable is damaged or the feed through is damaged any leak here would cause detector noise.

If the instrument is vented and the analyzer door is opened you'll notice there is black plastic knurled nut inside the analyzer door for this feed through. It is possible to slip the HED wire out of this, loosen the feed through and then remove and re-seat it. There is an o-ring in there.

If the o-ring is ripped or otherwise damaged it can burp or leak air here, and the high voltage to the HED will ionize the oxygen in the leak and cause detector noise.

I'd recommend having an FSE take a look at it.. but this could be a source of HED faults or detector noise. Typically if the leak is big it will cause an HED fault that aborts the run or the tune, if the leak is small it can cause "mass independent" noise (ie, a peak of some abundance at every mass.)