5972 Repeller Voltage

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

44 posts Page 1 of 3
I'm working on a work-from-home project that involves me doing a major upgrade to my 5971. I started out looking for a SmartCard II so that I could run G1701BA, but ended up buying a tested and working 5972 eMod. So, at least electronically, my 5971 is now a 5972(albeit with the cast/rough water-sucking manifold, fat chamber seal, and no lights on the front). I'm also running G1701BA B.01.00 in Win2K(with the instrument set as a 5972).

Before doing all of this, the source got a thorough cleaning with some "insight" courtesy of Geoff Wilson up in Michigan, who also sold me the eMod. On his advice, I paid a lot of attention to parts I don't often-in particular the edges of the draw out plate, the "step" where the plate sits, and all of the lens apertures.

On a 5971, the manual tells you to leave the repeller at 14.99V unless you have a good reason to do otherwise. Autotune in my experience holds it there. I don't have a 5972 manual(I'd be enormously appreciative if someone has a PDF they could share) but I've noticed that autotune for the 5972 seems to not follow this. Usually, the repeller ends up around 25V. The ramps tell me that that isn't anywhere near the voltage I should be using for maximum abundance.

Does anyone here either run or remember running a 5972 and if so, what your repeller voltages typically were? I'm wondering if I need to investigate something else, or if this is normal.
I would adjust the repeller on both the 5971 and 5972 to reach their maximum sensitivity. I believe the 5971 maxed out a lot lower voltage than the 5972.

With the introduction of the 5972 they began to allow the filament current to be adjusted like on the 57973 and up models, this allows you to optimize the repeller ramp profile, the 5971 had a fixed filament current. If you upgraded the main board you should now have access to the adjustable filament current so if the repeller doesn't give a bell shaped curve when ramping you can adjust the filament current until it does, then set the repeller voltage to the top of the curve and you get optimum response from the repeller.

Autotune on that software will usually optimize for largest abundance of m/z219, only if you run a target tune will it do more adjustment to the rest of the masses to pass either BFB or DFTPP. I normally ran autotune then manually adjusted the ion focus to get the ratios close, then used variable setting on entrance lens offset to tweak them in to pass tuning criteria. If you don't run EPA methods then you can tune manually to optimize for whatever mass range you are looking for.
The past is there to guide us into the future, not to dwell in.
Thanks James.

Yes, I do have access to the filament current adjustment. I ended up raising it to 61µA and got much better repeller ramps along with very nice intensities of 219 and 502(104% and 9.1%, respectively).

I'm not running EPA methods. My main interest is in generating "classical" mass spectra that will match library searches, which Atune generally does a good job of. None the less, I'm running target tune now.

Of slight interest, I've also been advised that I can fit 5973/5975 filaments with the 5972. The only ones I have are at work, so I haven't tested it yet, but I'll be interested to see how that works.

In all of this too, I was also "given" a GCD. I haven't done anything with it yet(it's sitting on the floor in my office, as it was too big to bring home with me), but I'm interested to play with it. About all I can find online is "don't bother with it" but I'm still interested in playing with it. It will apparently run with G1701BA, and of slight interest is that it uses the fused silica/gold quads like a 5973 and not the ceramic/silver of the 71 and 72.
I have never had to go that high with the current, but I bet if you put in the 5973 filaments it will run lower since the target on those is much better at drawing the electrons through the source than just using the opposing filament wire. I think that is one reason the 5970/5996 sources was so efficient, they used a large T shaped target behind the opposite filament to pull electrons through the ion chamber, plus the ion chamber in those was tiny compared to the 5971 and up.

Normally when you raise the filament current you get more breakdown of the molecule and thus it favors the lighter masses. Default in the 5973 is 35uA but I can get away with running it as low at 20uA with good results and longer filament life.

That is interesting about the quads on the GCD. If I recall it was pretty much a dumbed down 5971, with fewer tuning options but otherwise the same hardware.
The past is there to guide us into the future, not to dwell in.
I dialed it back to 50µA today and it was still tuning nicely with strong abundances at moderate EM voltage. I want to grab some 5973/75 filaments the next time I get clearance to go into the office and see what happens with those. Even if I did get more fragmentation(which I seemed to do) it seems as though overall ionization efficiency increases and I get a lot more total signal. That seems a useful tool to get a bit more sensitivity out of an instrument that otherwise struggles with LODs as compared to more modern instruments.

On an unrelated note, I actually now have everything I need to fit CI to this instrument(I have a brand new 71/72 CI source, a gas manifold, and all the plumbing bits and pieces) but don't know if I'm going to bother fitting it. My Varian 300 makes things a lot easier, and I'm also actually not going to be at my current workplace more than a few more months(exciting stuff that I won't go into here-email me for the story).

Time permitting, I do want to play with the GCD. As best as I can tell, it's more like a 5972 than anything. Among other things, it uses the nice 5972-style polished vac manifold that doesn't soak water like a sponge and also uses a nice simple O-ring to seal rather than the complicated 5971 stepped gasket. I've also been advised that the mass range tops out at ~500 m/z rather than 650 on a typical MSD, and tunes on the 441 peak rather than 502. I'll photograph it when I dig into it.

I know James that you've really spoken highly of the 5970 in the past. I really, really would like to get one. There's a nice one on Ebay in Lexington that's been there a year or better. It seems to have an SCII and the G1701BA update(and runs on the same Optiplex I'm using, which means that it's using the good 82350B card). Unfortunately, it's a bit more than I can swing-I keep hoping someone will clean out a lab, find one, and say "free if you come and get it"(we can give a donation letter on it) but that's probably my max budget.
Our 5970 was originally set up for the RTE-A mini computer then we upgraded it to the PC version which used either the SCII or SCIII. I remember it was a better comm card than the one in the 5971, so when the 5970 finally died I swapped the smart card from it to the 5971 so I could use Win95 or NT instead of Win3.11 that was a great improvement. If the 71 would have had the turbo pump of the 70 I think it would have been an improvement. The only downfall of the 71 was the silver tape on the quads, otherwise they were great instruments.
The past is there to guide us into the future, not to dwell in.
If I had the time to experiment, it would be interesting-to me-to put a GCD top board and analyzer in a 5971/5972. IIRC, the high mass limitation in the GCD was in the mainboard and not the top board.

GCDs seem few and far between these days, but are virtually being given away if you do find them(mine was given to me). I may try sticking the top board on this 5971/5972 if I get a chance, although I'd also like to run the GCD as-is.
I wonder, could you put the 5972 main board in the GCD and make it a 5972?
The past is there to guide us into the future, not to dwell in.
I've been told that's possible also.

The GCD does have the nice polished 5972 style manifold with the round O-ring.

The GCD really is just a 5890(with EPC) and a mass spec shoved together. They're not at all connected internally(other than by transfer line)-I know that the GC and MS each have their own HPIB connector, I think they have separate electric plugs, and IIRC there's even a sync cable. Mine's stuck at work for now so I can't actually look at it, but I at least want to pump it down and see how it works.
This discussion really interests me. How exactly did you upgrade from a 5971 to an effective 5972? I'd like to make my 5971 more effective.
LALman wrote:
This discussion really interests me. How exactly did you upgrade from a 5971 to an effective 5972? I'd like to make my 5971 more effective.


The 5972 eMod is plug for plug compatible and mechanically compatible, and the top boards are the same. If you can find a complete 72 eMod, it's probably an hour long job(not counting venting and pump down time).

The 72 eMod should also have an SCII or II+ in it. That was a lot of my initial motivation for going this route as you need the SCII or better for G1701BA, and the eMod was $1500 vs. ~$600 for an SCII.

I also put 5973 filaments in, which are a direct fit, tune with higher absolute abundances and do so at an EM voltage ~100V lower than a brand new 71/72 filament.
benhutcherson wrote:
LALman wrote:
This discussion really interests me. How exactly did you upgrade from a 5971 to an effective 5972? I'd like to make my 5971 more effective.


The 5972 eMod is plug for plug compatible and mechanically compatible, and the top boards are the same. If you can find a complete 72 eMod, it's probably an hour long job(not counting venting and pump down time).

The 72 eMod should also have an SCII or II+ in it. That was a lot of my initial motivation for going this route as you need the SCII or better for G1701BA, and the eMod was $1500 vs. ~$600 for an SCII.

I also put 5973 filaments in, which are a direct fit, tune with higher absolute abundances and do so at an EM voltage ~100V lower than a brand new 71/72 filament.


If you can only find spare parts, you need to replace the power supply with a 72 power supply, which is a little more stable and rugged and was automatically done by any repair tech once the 72 came out. The other parts would be a 72 main board and the SCII. I can't remember if the SCIII fits those or not. I do remember we had a 5970 that had been upgraded to work with W95 MSDChemstation and when it died I took the SC from that and put it into the 71 we had to be able to use the Win95 version instead of the W3.11 version. Those are really the only three parts that are different between the 71 and 72.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
If you can only find spare parts, you need to replace the power supply with a 72 power supply, which is a little more stable and rugged and was automatically done by any repair tech once the 72 came out. The other parts would be a 72 main board and the SCII. I can't remember if the SCIII fits those or not. I do remember we had a 5970 that had been upgraded to work with W95 MSDChemstation and when it died I took the SC from that and put it into the 71 we had to be able to use the Win95 version instead of the W3.11 version. Those are really the only three parts that are different between the 71 and 72.


I'd have to look at them side by side which I can't easily do at the moment, but I'm not 100% sure the standoffs are the same on the 71 and the 72 mainboards.
If nothing else, the electronics module cover on the 72 is two pieces and a single piece on the 72, but I don't think this would actually make any operational difference.

I don't think an SCIII, which is LAN, will work with a 72, but I could well be wrong on that. There are three revisions of the SCII(the original, SCII+, and SCII++) and from a bit of reading it seems that the SCII can occasionally be buggy with the later versions of Chemstation. I'm not sure how correct that is, but I've had a couple of "true" 5971s on G1701BA and plain SCIIs that were fine.
benhutcherson wrote:
James_Ball wrote:
If you can only find spare parts, you need to replace the power supply with a 72 power supply, which is a little more stable and rugged and was automatically done by any repair tech once the 72 came out. The other parts would be a 72 main board and the SCII. I can't remember if the SCIII fits those or not. I do remember we had a 5970 that had been upgraded to work with W95 MSDChemstation and when it died I took the SC from that and put it into the 71 we had to be able to use the Win95 version instead of the W3.11 version. Those are really the only three parts that are different between the 71 and 72.


I'd have to look at them side by side which I can't easily do at the moment, but I'm not 100% sure the standoffs are the same on the 71 and the 72 mainboards.
If nothing else, the electronics module cover on the 72 is two pieces and a single piece on the 72, but I don't think this would actually make any operational difference.

I don't think an SCIII, which is LAN, will work with a 72, but I could well be wrong on that. There are three revisions of the SCII(the original, SCII+, and SCII++) and from a bit of reading it seems that the SCII can occasionally be buggy with the later versions of Chemstation. I'm not sure how correct that is, but I've had a couple of "true" 5971s on G1701BA and plain SCIIs that were fine.


We replaced that 70 back in 1996 so the memory on which version it was is a little dusty :) SCIII must have been on the early 5973s if it is for LAN.
The past is there to guide us into the future, not to dwell in.
(1) I've just checked and I have the Smart Card II but not the + or ++. Is it just the software upgrade that lets you modify the filament voltages, or must one replace the top board?

(2) Does the source have to be modified to let you use the 5973 filaments?

(3) I'm running G1701AA A.03.00 on windows 98.

(4) So, I gather from rereading the thread, I would need the 5972 main board? I suppose that has the electronics that let you change the filament voltages.

(5) Are you able to sucessfully run the 6 mm inert drawout plate on your setup? I decided to try it in mine and ION FOCUS is all over the place. It can't get the same trace twice. I also changed out the entrance lens insulator from the two piece to the one piece (what a pain) and I wonder if that has anything to do with it.
44 posts Page 1 of 3

Who is online

In total there is 1 user online :: 0 registered, 0 hidden and 1 guest (based on users active over the past 5 minutes)
Most users ever online was 1117 on Mon Jan 31, 2022 2:50 pm

Users browsing this forum: No registered users and 1 guest

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food & Beverage, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry