5973N tune issues

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

66 posts Page 3 of 5
I'm not certain. I can see the filament in the center lit and the gauge reads correct after a few minutes(2.9E-5Torr) but it seems very dim to me but I haven't run this instrument much before I have a 5975 so I don't really have a frame of reference. I had maintenance replace the filter caps so they should be good and I only keep it on for a little bit at a time when I want a reading. Are you supposed to keep it going constantly? It would probably just overheat and kill the caps again.

There was some stringy/rubbery brown crap in there that I rinsed out with MeCl2 and methanol.

I am still waiting for the detector. I ordered the ETP one from Restek. I don't suppose there is a chance the electron multiplier is still good. My 5975 is getting close to needing a new multiplier in the next year or so.
Still waiting for the new detector. I tried a tune again today and it is weird the first few screens look good then then PFTBA and sensitivity quickly goes away to nothing. I was reminded of James Ball's post about the calibrant valve closing but that wouldn't explain the poor sensitivity when i run stuff through the GC. FSA is sure that the detector is failing as it is run longer.
MSCHemist wrote:
I'm not certain. I can see the filament in the center lit and the gauge reads correct after a few minutes(2.9E-5Torr) but it seems very dim to me but I haven't run this instrument much before I have a 5975 so I don't really have a frame of reference. I had maintenance replace the filter caps so they should be good and I only keep it on for a little bit at a time when I want a reading. Are you supposed to keep it going constantly? It would probably just overheat and kill the caps again.

There was some stringy/rubbery brown crap in there that I rinsed out with MeCl2 and methanol.

I am still waiting for the detector. I ordered the ETP one from Restek. I don't suppose there is a chance the electron multiplier is still good. My 5975 is getting close to needing a new multiplier in the next year or so.
The light from the tube is about identical in color to that from a candle flame. Although, as you noted, dimmer.
I leave my two triod vacuum gages on 24/7. Mine ran for about 10 years before the caps failed. At 1mL/min Helium flow (standard turbo pump & E2M2 rotarty pump) I am seeing (2.9E-5Torr). My detector is also an ETP but I got it overnight from FSA.
Got the new detector in and installed it. I am going to let it stabilize overnight but I don't know how this is possible but the triode tube is a LOT brighter and less drifting with the new detector.
MSCHemist wrote:
Got the new detector in and installed it. I am going to let it stabilize overnight but I don't know how this is possible but the triode tube is a LOT brighter and less drifting with the new detector.


Could be there was a slight leak somewhere before, who knows.

I like the ETP multipliers, but always have to manually set them to about 900V when they are new, the stock ones run about 1200 so the tune can be a little flakey when autotuning the first time.
The past is there to guide us into the future, not to dwell in.
We'll find out tomorrow morning. You mean you go into manual tune and inputting 900ev before starting autotune? I'll try that. I'm hoping the EM horn is salvageable for my other instrument. The detector looks a bit old mainly the copper that brushes up against the horn. The horn looks ok it doesn't take much effort to pop it in and try it. The ETP is a completely different set even new wires and nuts.

Yea the triode is very bright now. It is running 2.1E-5 when I left it. guage feels bit warm though. There was a residue of oil on the inside of the door under the detector mount but no sign of oil on the quad housing, source or any internal parts fortunately. Just wiped it off with methanol (so it must be santovac Inland is hydrocarbon). I took the whole door off the change the detector (you pretty much have to).
It's been a while since I've worked with a 5971 or 5973 with an "exposed" vac gauge(my 5975 has the Granville-Phillips micro gauge).

At the same time, though, we have two Voyager MALDI-TOFs and the ion gauges on those are left on. The filaments on them are fairly bright-I'd say comparable to filament on the 5975 at an i.e. of 70EV.
Well now I have absolutely nothing. I tried a tune and saw nothing. I can tell from the vac guage PFTBA got in there but all I saw was noise no peaks of any kind and then it quit saying peak widths to narrow. I was careful installing it making sure none of the wires were shorting/touching anything.

I am probably going to take the new detector off and put it on my 5975 which is about due so it won't be a total waste so it would appear it must be either a side board or main board issue.
If you have good vacuum and can see the pressure increase when the PFTBA is open then the absence of peaks usually means side board problem, either control of the quads or the filaments. Do new filaments show ion burn after being on a while? If you can see that it means the filaments are powering up.

When the quad drivers are going out the first sign is usually peak widths that get wider or narrower over time as it scans, causing you to have to retune often to keep the peak widths in check.(usually seen by losing or gaining the small masses next to the large ones like 173 and 175 versus 174/176 for BFB or 441 and 443 versus 442 for DFTPP) Once that quad driver is gone you can form peaks when scanning, it just lets everything pass through or everything gets rejected so signal is just grass.

If you have another 5973 or 5975 you can swap the side board and see if that fixes it as a way to diagnose. I have also taken the entire door from one and put it on another just to see if the problem follows or not.
The past is there to guide us into the future, not to dwell in.
FSA is still sure it is the detector and the ETP is bad. The paperwork in there from Restek gives a test date of 2010 so it may be too old. Nevermind it looks like it was retested in 2018 even though it was produced in 2010.

I'm honestly starting to see that scene from the movie Office Space where they take the evil printer into a field and go at it with a baseball bat in my head.
I put the old detector back in for now and I have signals albeit weak and fluctuating ones. If my old 5975 detector doesn't work probably next week then I am just going to send the sideboard out to Astra Scientific. They say they can fix them for $1800 with verified tune report.
So my plan is to put the new detector in my 5975c which is almost due. The detector is ~2000 and is OEM so about 12 years old then take that one which I know works and put it in the 5973. I am fully convinced this is a fruitless exercise but it will finally eliminate the detector.

That brings me back to either sideboard (probably) or main board. Sideboard back to either replacing it for ~2-3k or Astra Scientific will fix it for $1800 and send a verified tune report. At this point I'd really like to send the whole analyzer out for repair and tell them don't send it back until it tunes but I guess FSA doesn't like to do that anymore.
Although this doesn't explain the low sensitivity with injected stuff I think I may have the same issue as James Ball with the calibration valve closing during tune.
viewtopic.php?t=46621#p223251

I ran the tune again today. The vacuum went from 2E-5 to 4E-5 and the first couple tune screens were good. Then it went back down to 2E-5 the ions went away. I got the the usual small noise peaks.

I tuned my 5975 and the vacuum stays at 4E-5 throughout the tune.

The question is why would a calibration valve close during a tune as opposed to just sticking closed. Do you think I can take it off and try rinsing/sonicating it with some methanol if it is gummed up?

BTW it always clicks and sometimes the vacuum reading doesn't change and it doesn't show good tune screens at all. Thanks for staying with me through this thread btw.
If you check that tune valve be very careful of not breaking the venturi tube that controls the rate of vapor delivery.

I have an anecdote from my ICP-AES days. A flow controller in the gas drawer started leaking a tiny bit of oil. The vapor from this oil was getting into the nebulizer venturi where it would coat the inside of the venturi and it would then misbehave and become variable and noisy. So, could the PTFBA vial be contaminated or leaking in air?

If solonoid "weakness" is suspected.... Maybe you could check the voltage being sent to the solonoid to see if its dropping or being cut off, as the PTFBA signal drops out.
I tried to tune it again today and same thing pressure up tune looks good; looks good; pressure returning to pre-tune levels and ions getting smaller and smaller until just faint noise peaks remain.

I'm wondering if it is just gummed up, some PFTBA gets in, it clogs, you wait a while then the PFTBA vaporizes so the next time you tune the cycle repeats.

I understand there is a metal frit with micro-pores that controls the flow?

If I am going to take it off and sonicate it in Methanol I need to know for sure though.
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