HP 5971 Ramping Source

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

17 posts Page 1 of 2
Can anybody direct me to a link that will show what an HP 5971 source should produce when ramping Xray, Repeller, IonFocus, EntLens, and EntOffs?

I am getting curves that do not resemble those I get on my 5973 MS. Standard tune gets me:...
Xray of 81.2
Repeller 14.99
IonFocus 44.0
EntLens 19.07
EntOffs 9.54
and EMVolts are at 1965

Ramping Repeller looks pretty normal with mass 69 peaking at 10, mass 219 peaking at 12 and mass 502 would peak at about 20.

Ramping IonFocus gives 69 and 219 stacked at 25 and mass 502 at about 40.

Ramping EntLens gives mass 502 at 25, mass 219 at 50 and mass 60 is a straight line rising from 0 at left to a maximum at max EntLens. On a 5973 these would be stacked more closely and perhaps mass 50 would give a straight line if the lens stack was dirty.

Ramping EntOffs gives Mas 502, 219 and 69 closely stacked at offsets of 12, 15, and 20 respectively.

I've cleaned and polished this source several times with no improvement. Is my EM too close to end of life?
If you have 300,000 counts for 69 then the EM should still be ok. The higher it tunes thought, the less linear range you will see, but it is still very functional even at 1900V.

The only ramp that seems odd is the entrance lens. Normally I would think it begins near max at left and peaks with just a few volts, then fall off pretty quickly as the voltage increases. We always ran with the entrance lens at 0 and if we had to add voltage we knew we had to clean the source. Two things can happen to the entrance lens, either the pin can come loose, or the brown vespel insulators can become contaminated and need replacing. If the insulators begin conducting you can bleed voltage over to ground or possibly from the ion focus, which will cause things to act strange. Also if you have the two piece insulator instead of the newer one piece, make sure the set screw that holds those lenses in place is not passing between the insulators and grounding a lens or that the pins have shifted and are grounding.

The x-ray lens is the same as the HED on the newer models, high volts on that should be ok, it is just the deflector than turns the ions towards the EM as they exit the quads.
The past is there to guide us into the future, not to dwell in.
If I have time tomorrow, I'll try to do a full set of ramps and show what they look like.

I don't know how "correct" mine will look, but at least it will give you some basis for comparison. I do know that they look quite different from what I'm use to on the 5975.

I do know that even though I can manual tune to give appropriate abundance for 502 with a width of ~.55, my 502 ramps are often still very noisy. Also, many of the 69 ramps will seemingly peg the detector. I can't give specifics now-I'm not a big user of ramps in general-my main use for them is creating custom tunes for SIM.

FWIW, my most recent EM tune is 1494V. I'm using an ETP discrete dynode EM(what was in the instrument when I brought it back to life after 10 years out of service).
Another thing to remember is every instrument is unique. While most follow each other in how they behave, some will give ramp profiles that look totally different from another sitting right beside it. It is always difficult to get supervisors who have no MS experience to understand, but if they have every played guitar or other musical instrument they can begin to understand that each will be a little different and is probably why we call them instruments instead of machines :)

When I first began doing MS I spent a lot of time in manual tune. We had a 5970 and two 5995, which are basically identical on the MS side. They were on the old RTE-A Chemstation, mostly text based, but lens ramps were graphical and it only had a basic Autotune function. To hit a BFB or DFTPP tune you had to manually tune. To make it second nature you have to look at the ramps more from a 3D point of view, you have three variables separated in two dimensions that affect the third dimension which is the percentage that each relates to the other. If the ramp lines are converging then the percentages will be getting closer to each other, if the lines diverge then they are getting farther apart. It drives most of the new MS operators crazy when they spend a hour trying to make a tune pass and I can look at the ramp and move one lens a few volts and it hits. Of course there are the times when it takes a lot of adjustments and that is the best time to train them.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
If you have 300,000 counts for 69 then the EM should still be ok. The higher it tunes thought, the less linear range you will see, but it is still very functional even at 1900V.

The only ramp that seems odd is the entrance lens. Normally I would think it begins near max at left and peaks with just a few volts, then fall off pretty quickly as the voltage increases. We always ran with the entrance lens at 0 and if we had to add voltage we knew we had to clean the source. Two things can happen to the entrance lens, either the pin can come loose, or the brown vespel insulators can become contaminated and need replacing. If the insulators begin conducting you can bleed voltage over to ground or possibly from the ion focus, which will cause things to act strange. Also if you have the two piece insulator instead of the newer one piece, make sure the set screw that holds those lenses in place is not passing between the insulators and grounding a lens or that the pins have shifted and are grounding.

The x-ray lens is the same as the HED on the newer models, high volts on that should be ok, it is just the deflector than turns the ions towards the EM as they exit the quads.
I agree that the entrance lens ramp is the odd one. Its a two piece and the pins are good I think. I'm pretty sure that the set screw is not touching either lens because I pinch them together at that side and then spread them at the two pins just in case they moved. So, it seems likely the 2 piece vespel insulator is being conductive. I've never put them in solvent but perhaps some alumina dust got on them. Perhaps also, the pin is grounding out somehow. I'll break vacuum and check it all out again.

Why is it that the vespel on the repeller can be put in solvent but not the lens insulators?. Different formulations I suppose.

I too am using an ETP Active Film Model LS516 electron multiplier.

Thanks for the help guys.
Are you sure the entrance lens is two piece, or the ion focus? Entrance lens is the one with the flat disk and the snout that fits into the quads, the ion focus is the cup shaped one between the draw out plate and the entrance lens.

Make sure the wires aren't reversed on those two, I have done that before and had weird ramps.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
Are you sure the entrance lens is two piece, or the ion focus? Entrance lens is the one with the flat disk and the snout that fits into the quads, the ion focus is the cup shaped one between the draw out plate and the entrance lens.

Make sure the wires aren't reversed on those two, I have done that before and had weird ramps.
Oops, I see what you mean. I misunderstood you. The ion focus is one piece (not two like benhutcherson's) and the entrance lens shaped as you said is the other piece. I thought when you were referring to the two pieces; you meant the ion focus and entrance lens held in the vespel insulator.

I made sure to trace the wires for the ion focus and the entrance lens to make sure they were connected correctly when I assembled them. I vented Friday and I will tear it down and inspect it this morning.

After talking it over with my electronics guru, I ordered a new lens set insulator Friday. We shall see if that helps.
I have disassembled the source after first carefully checking that the right leads were attached and checking for shorts. The set screw is not shorting, the posts attached to the two lenses are firm and electrically continuous. I'm not getting any conductivity from the vespel holders.

The only thing out of place is that the entrance lens is somewhat loose when the whole thing is assembled. It can be rocked back and forth by grasping the end of the entrance lens. It appears that the vespel is not gripping it tightly enough to hold it tightly still. Swapping the insulators top to bottom makes no difference. The entrance lens is a bit loose.
Just thought I'd comment that after a bit of thinking, I began suspecting that the EM was EOL in mine. Even though I could manually tune it to ~1500V, and Quicktune would work, I never could actually get it to complete a full "standard spectra auto tune." I'd been running it anyway since I was able to get a good manual tune.

In any case, I had a spare ETP 14516 multiplier that came in the "spares" box with the instrument. I had wondered if it was used, but I gave it a good look-over today, and it appeared new. The documentation in it was dated to 2009, the multiplier was still in its dessicant-sealed ziplock bag, and the SN on it matched the SN on the box. So, I took a chance and swapped them.

When I left work for the day today, I was still waiting for the analyzer to reach its normal ~170º operating temperature. Still, though, it completed an autotune at ~1300V(it initially took a lot of messing with manual tune to get it close, but I think that was from not letting it settle enough after breaking vacuum). The ramps also look a LOT more like I'm use to seeing, with a nice Gaussian distribution for most of the values. I'm going to be interested to see what an autotune looks like tomorrow after it sits overnight.
Mine was able to tune but had hard time. Maybe that will improve when I put in the new vespel lens insulator. By the time it passes stune, after I let it settle for 10 minute so; generating a report gives a couple million counts on mass 69. So I turn down the EV a bit but not much because if I leave it in profile mode for a few minutes, mass 69 drops down to 5-600K.
LALman wrote:
Mine was able to tune but had hard time. Maybe that will improve when I put in the new vespel lens insulator. By the time it passes stune, after I let it settle for 10 minute so; generating a report gives a couple million counts on mass 69. So I turn down the EV a bit but not much because if I leave it in profile mode for a few minutes, mass 69 drops down to 5-600K.


If the calibration valve stays open for a while the PFTBA will finally come to equilibrium with the vacuum and give steady counts. When I tune I normally open manual tune and set it to scan and let it go for 5-10 minutes until I see the counts for 69 become constant, then I begin with the autotune. That always seems to give a more reproducible result than letting it tune immediately after sitting overnight.
The past is there to guide us into the future, not to dwell in.
The new vespel source lens insulator just arrived and it is indeed a 1-piece. It looks like a slightly different material than the original 2-piece insulator. It does hold the entrance lens more rigidly. My 5971 is pumping down right now and we shall see if tuning is improved tomorrow.
If yours is anything like mine, the tune tomorrow may be somewhat less than satisfactory, but it's still worth a shot.

Looking back over the various 5971s I've worked with over the years, I had one that would usually tune decently in the afternoon after pumping down all morning. The one at work definitely likes a few days.


BTW, the "new" EM did make a big difference for mine, and although a few of my ramps still look noisy they are mostly clean. I need to run some samples through it-I actually haven't had a chance to since replacing the EM.
The tune today is awful. Its as if the new vespel evaporated junk all over the lens stack. The lens ramps are super jagged. I'm going to have to break vacuum and clean again but I'm going to leave it hot over the weekend to bake out the vespel.

Still looks like entrance lens ramp of 69 is a jaggy straight line; not a gaussian curve.
I've cleaned the source and its going back under vacuum right now. That one-piece vespel insulator is really hard to disassemble! I was afraid I would break it and it cost $370, sheesh. The lens surfaces all looked clean but the body was blackened around the filaments. So, I guess something cooked off from the inlet or the vespel. I found a pdf that shows how the 5973 looks for each lens ramp. I'm linking it here manually_tuning_gcms_with_chemstation.
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