Converting 5973 to Turbo Pump

[benhutcherson]

I have a project I'm about ready to take on while my 5973 is down for other reasons.

I appreciate how "set and forget" the diff pumps are, but they do have their issues with slow pump down speed, backstreaming, and especially with the undersized roughing pumps Agilent loves give worse ultimate vacuum than turbopumps(that's not as much of an issue with the older larger rough pumps, and I know I can run a bigger pump-I have but it's not really an option for me at the very moment but I hope soon-in a past job when I temporarily switched my 5975 from its E2M1.5 to a Varian DS102, which is comparable to an Edwards RV3 and actually a higher spec pump than an E2M2, I'd reliably see hi-vac in the mid 10^-6 torr range with the diff pump, where the best an E2M1.5 could give was 10^-5).

Of course the 5973 and 5975 were built with both, and the eMod is capable of controlling both. Of course conversion isn't 100% straight forward-the diff pump manifold uses a KF-50 flange to attach the pump as well as baffles in the bottom to(supposedly) minimize backstreaming/oil spattering. The turbo has a wide open hole in the bottom of the manifold(you'll see a screen there with the turbo installed, but that's part of the pump) and the flange is larger and not a KF type.

The eMod can control both. The board I've heard Geoff Wilson call the "Power Back Board"(the one where the AC in attaches) has two ports of relevance here-"Hi-Vac Power", a round locking connector, and "Hi Vac Control", a DB-25 connector. On a diff pump instrument, a cord runs from "hi vac power" to-presumably-to the diff pump heaters. Diff pumps have a Convectron gauge on the foreline to pump connection, something not present on diff pumps, and this along with the diff pump temp sensors("hot" and "too hot") connect via the DB-25 connector. I think the front fan on the instrument(that cools both the diff pump and turbopump) connects here along with the speed sensing wire. A turbopump instrument of course has the turbopump mounted on the manifold, then the pump controller mounted behind it tucked up under the manifold. The pump controller obviously has a cord from the controller to the pump. The DB-25 runs from the controller to eMod. The controller also has a power in connection(looks like a standard computer power plug) that on some instruments-but not all I've looked at on Ebay(and I've looked at a lot) has a cable running from here to the "Hi Vac Power" round port.

Not too terribly long ago-and on my own dime since money is tight at my current place of employment-I bought a "for parts but powers on and pump spins up" 5973 turbo pump instrument. It's a first gen HPIB instrument, the same age as my current one.

My current working 5973 started life as HPIB, but Geoff/GLTS came in and did the "budget LAN conversion" where he installed a LAN SmartCard III in the original eMod(plus fitted a JetDirect to the 6890, sold me a G1701EA license and provided a computer with it pre-installed).

Once I have this parts 5973 in-hand, my plan actually is to transplant my eMod and known good sideplate/analyzer(I will test the one with this one to see if I have a working spare of course) and hopefully have a functioning turbopump instrument.

As a question for those of you who may have experimented with this-I like measurements and gauges, and will be sorry to lose the Convectron on the diff pump even if it's an overall positive upgrade. Looking at the DB-25 plug, it looks like the diff pump only uses a few of these pins, presumably a few of which are used to read the Convectron. Is it possible to leave this in place and "tap in"(using a DB-25 splitter, which I could build if I were so inclined) and have the instrument read it? Of course too if I really want it, I realize that it's presumably a Granville-Phillips 270, and presumably I could use a stand-alone gauge controller to read it. Still, though, reading through software would be nice. I don't know, though, if the MS/Chemstation is even capable of handling both streams of data, though-I know turbo instruments report turbo speed instead of foreline pressure, and will Chemstation fall over itself if it has both? I can't imagine that it uses the same pins in the DB-25 connector, since for the convectron it really just is a wire harness and presumably there's a gauge controller buried somewhere in the eMod. I know Agilent considers the data redundant, but I know I certainly appreciated having both manifold vac and foreline vac when I was running a Varian 300TQ MS(which also reported source pressure to me for CI purposes collision cell pressure for CID... but that was also a totally different beast in a lot of ways).

Also, as a bit of an add-on to that and possibly a stupid question-does the Convectron need to be mounted with the tube vertical? I could see that being the case, plus HP/Agilent makes sure it stays that way and it seems as though on the broader market they make about a dozen different configurations of this gauge. At one point I had a many-hundred page manual from Granville-Phillips that discussed the 270 and other Piranni-type gauges in great detail, but I can't locate my download of it and it seems to have disappeared when Granville-Phillips became MKS. If that's the case, it may take a bit of creativity given that the diff pump exhaust turns 90º "up"(and the gauge mounts on top of this) and the turbo pump comes straight out the base of the pump.

Last thing too-if anyone else has done this conversion, did you have to change anything in the eMod? Geoff mentioned there being some difference in settings in the power back board and suggested comparing those boards in my diff pump instrument and turbo pump instrument. I don't have the turbo in hand yet, but all I could find that might point to something on my current eMod is a bank of 4 pins in a line with a jumper that's labeled "Diffusion pump power." It's currently in the center position. I'm wondering if, perhaps, the jumper block is removed completely or moved to the lowest position if the pump controller is powered through the DB-25 connector, or perhaps moved to the highest point if the pump controller gets power through the "hi vac power" port but I'm purely speculating. I seem to recall that the diff pump runs on 40V, or maybe that's a number from somewhere else. Does anyone know if anything needs to be done here? Obviously I'll compare, check, etc and even swap power back boards if necessary, but wanted to ask. I couldn't find anything else on the power back board, the tororoidal transformer, the front power board in the emod, or mainboard that would point toward a difference between diff and turbo pump, but wanted to ask if anyone knows this.

I will report back with my results! I do finally have a vac gauge controller, so can back up my changes/reports with a real numbers...

[benhutcherson]

I'm happy to report that everything more-or-less went fine. The MS finally arrived Tuesday, I set it up and was able to get things going without too many teething pains. For now I'm running it on HPIB as I haven't transplanted my LAN-converted eMod over, but all is fine otherwise.

I only really had one hiccup. I should have caught this, but I was missing the power cable that runs from the eMod to the turbo controller. This has a multi-pin locking plug on the eMod end(it's an AMP branded connector-been looking to find one) and a C13 plug(what I call a computer power plug) on the other end. The PN on it is G1099-60435-feel free to look that up with Agilent and scream.

I texted Geoff, wondering if I could use a computer power cord to plug the turbo pump controller directly into the wall. While I was waiting on his answer, I started poking at the pump power connector with a voltmeter and noticed that most of the pairs of pins I poked that gave any voltage at all read 120VAC. So, I took a chance and just plugged the turbopump controller directly into the wall. Geoff wrote back a few minutes later to tell me that what I'd already done would work

It's fine now as a stop-gap, but I've exchanged a few texts back and forth with Geoff where's provided me photos of a cable and pin-outs. I tracked down the connector at Digikey(it's an expensive bugger-around $15 for the connector, $15 for the back shell, and the pins are $1.50 or so each), and am going to build a few of these cables. I've actually ordered 10 connectors since that drops the price/connector down a decent bit, and figured I might do more than a few folks a favor with these. Fortunately the other end is cheap-I just sourced some 18AWG computer PSU cables on Amazon for about $2 each and will chop those off. Apparently also the same basic configuration cable comes in a few different lengths-I'm going to send Geoff two at 14" long, even though I think he said the G1099-60435 is around 10".

Unfortunately I went in on Monday and the tune had gone all to heck. I'm afraid I left some crud in the filament holes that's causing issues. I REALLY think that because I see a dramatic difference in abundance(like a couple of orders of magnitude) between filaments 1 and 2. Autotune got the EM up to 2400V(it had been tuning at 1350 or so) to get abundances where it wanted and failed-I was able to get them okay-ish in manual tune, but with terrible peak shape. At one point I vented(it's so nice how quick that is with a turbo, even though it does take the source a while to cool), took the source apart and gave it a quick swab, and swapped the filaments between two positions. The filament 1-2 discrepancy remained(it followed the position, not the specific filament). I'm wondering if the issue is in the hole for filament 1, but that's also messing with the electron maybe to a lesser degree even with the other filament since-as I understand it-ideally the electrons will reflect off the guard behind the other filament and make another pass back through(if that makes sense). I'm not sure if I have that design understanding correct.

I'm not sure too why it tuned so nicely the first day, then fell apart, unless it was crud migrating after the source came up to temp. Per SIS's publications, I actually cleaned the last time with a Dremel and rouge, and I'm wondering if I had a bit of left over rouge migrating. I don't have a sonicator here, so had used the old trick of boiling in solvent, but I don't think this is anywhere near as effective as ultrasonic. I just need to bring my one from home in-a Harbor Freight unit that I've had for close to a decade now, and has cleaned cartridge brass, car parts, fountain pens, circuit boards, and plenty of other things as I've needed to over the years. It should do the job for this.

We're shut down for Christmas, though, so before leaving I actually plumbed hydrogen into it-I'd been running it on hydrogen for years, but had recently switched back to helium as I'd gotten frustrated with things like the(apparent) peak tailing of hydrogen and some of the other issues. I know, though, that hydrogen can clean sources to some degree, so once back in I'll turn it on and let it scan in manual tune with a good flow of hydrogen for a while and see if things improve. I know probably the real solution is to just vent and clean the source-again-but this will hopefully give me some idea as to whether or not this is the problem/. I'm hoping this is the case, and it's not an issue elsewhere in the system(I do have a complete sideboard/analyzer less source from the parts system, but haven't tested those yet).

So, that's where I am. I'm just happy that I have a working turbo system. Of course the ion gauge itself is a recent addition, but with the diff pump and E2M1 I'd see ~2x10^-5 torr with a blank ferrule, and with the DS102 I'd see 1.1x10^-2 with a blank. With the turbo and E2M1 it will flirt with 1x10^-5 with resting flows(helium). The DS102 and turbo gives around 7x10^-6 with resting flows of helium, and 1-2x10^-5 at 1-1.5mL/min analytical flows. This was actually before I really did a thorough job of cleaning and greasing the manifold gasket, which I did on Monday, so we'll see how it pans out after sitting under vacuum for a few weeks. And yes I realize I can't directly compare high vac readings with a blank ferrule to ones with column flow-presumably blank ferrule readings are "real" since what's in the analyzer would be air which IIRC is usually listed as responding close enough to N2 to be interchangeable, while H2 and He do give different responses. For some reason I have .6 as the conversion for He in my head, and am not sure what it is for hydrogen(and MKS vacuum seems to have gotten rid of all the wonderful data that Granville Phillips use to provide).

[mathieu_stability]

Hi Ben

I,ve just seen your thread regarding a 5973 conversion from diffusion pump to turbo.

In my experience working on this instrument, I would say the following:

did you swap the PFTBA solenoid valve body ? diff and tiurbo have different sized internal restrictors and are labelled D or T

was the ceramic source board swapped ?

use of vacuum grease... No, not necessary.

would be interested to hear if MS is currently operating. Matthieu

[mathieu_stability]

apologies Ben. I see in later threads you have already addressed the PFTBA valve issue.
That aside, is the MS operating as expected ?
I have done this conversion on a number of sites here in the UK