Nitrogen at 1200% of m/z 69

Hi guys, I've got a 5975 that was vented for around 2 months due to the whole helium thing. The analyzer chamber was sitting at ambient for the duration, multiplier was still pretty new so I did some maintenance and pumped it down to try and save what was left of it. I tuned it 2 days later and I'm seeing a huge nitrogen peak. 69 is at ~620k counts and 28 is around 7.5 million, I don't think the turbo would even spool if it was this bad of a leak. I sprayed the door and mass spec inlet with duster and didn't see a spike on mass 51. Vacuum is reading 7.12e-6, does it just need more time to pump down since it was vented for so long or am I missing something here?

Thanks,

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  • What is the O2 level you're seeing?  If it's an air leak, the N2/O2 ratio will be approx. 4.  If the O2 level is really low, then it's either a big leak before a gas filter (filter traps O2 but lets N2 pass) or a gas supply problem.  I have seen a customer accidentally connect a N2 cylinder instead of He - both use a CGA 580 fitting so it's an easy mistake to make.

  • Running off an 8 tank helium bank, instrument further down this T off the main line looks fine. I've been up and down most of the connections with a leak detector including split vent line and I'm not seeing anything. Main bank hasn't indicated a leak since I opened this line. Oxygen is negligible, it looks better this morning but still not ready to run injections.

      

    I'm kind of starving it right now with a total flow of 5.4 mL/min and I've seen water climb when you do that. I loaded a run method for a couple hours yesterday but it didn't do anything for my nitrogen count.

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  • Running off an 8 tank helium bank, instrument further down this T off the main line looks fine. I've been up and down most of the connections with a leak detector including split vent line and I'm not seeing anything. Main bank hasn't indicated a leak since I opened this line. Oxygen is negligible, it looks better this morning but still not ready to run injections.

      

    I'm kind of starving it right now with a total flow of 5.4 mL/min and I've seen water climb when you do that. I loaded a run method for a couple hours yesterday but it didn't do anything for my nitrogen count.

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