Varian Saturn 2000 GC/MS

[erica]

Hi all,

I've been having problems with my system. First I was getting spiking peaks, so I thought the trap was dirty and opened the system to clean it. I saw by that time, that the filament was bad, so got it changed.
Now, everything seems fine, the tune passes, but the diagnostics didn't pass. When I try to go to acquisition I get the message that a multiplier set is required (but my multiplier is pretty new, it was changed last December). However, if I load the method and click to reset the MS I am able to run by starting it on the GC panel.
I just don't know how to get start troubleshooting it.
Thank you all for your attention.


Erica

[Ultimate Science 101]

Hello Erica --

Under the AutoTune tab in MS Workstation, have you recently tuned your electron multiplier? If so, what is the voltage coming at? If you click the setpoints tab, you should be able to see what the last successfully tuned voltage is.

Regarding this specific error message, try re-tuning your multiplier if you haven't done so recently and see if the message goes away when you run the diagnostics again. If not, can you post the specific message you are seeing?

Good luck!

[erica]

Hello ,

Sorry for the late reply. I was away from the system for one week, and of course, the problem is still there.
I tuned the EM, and the voltage is 1500 V. The diagnostics still gives me the error message and the dialog tab gives me "electron multiplier set required" every time I try to load a method. However, if if click "reset" under the MS tab, I am able to run the GC manually.
I don't understand very well what is the problem. I had the system opened and the EM reinstalled, but still the same problem.

Thank you very much for you attention and help.

[Hornet]

Hello ,

Sorry for the late reply. I was away from the system for one week, and of course, the problem is still there.
I tuned the EM, and the voltage is 1500 V. The diagnostics still gives me the error message and the dialog tab gives me "electron multiplier set required" every time I try to load a method. However, if if click "reset" under the MS tab, I am able to run the GC manually.
I don't understand very well what is the problem. I had the system opened and the EM reinstalled, but still the same problem.

It probably didn't tune correctly. What does the log say (under Auto Tune) before it tells you the final EM Voltage? Copy&paste the log.

[sideline]

Hello,

I am having a similar problem to Erica above and was hoping one of you could help me find a solution. My system says electron multiplier set required. I have inspected the set and cannot see any damage. A service engineer came out in April and he said all the components in this part of the machine looked fine- I know some time has passed since then but my samples are the first to be run on the system since then. Like Erica, when I click on Reset in the aquisition tab I can run samples but does this do the system any damage? Even if it does not- are my chromatograms to be trusted?

I'd be really grateful for any help you can give! I have included all the outputs I could think of that might be relevant below.

Cheers,

Aoife

The diagnostics test is as below, the waveform test usually does not fail but it did the last time I did it:
14:04:22 Basic Hardware Test: Passed
14:04:22 Vacuum Test: Passed
14:04:22 RF Test: Passed
14:04:22 Waveform Test: FAILED
14:04:22 THE WAVE GENERATOR IS DEFECTIVE (NOISE FAILURE). LIKELY CAUSES INCLUDE THE
14:04:22 MANIFOLD ELECTRONICS ASSEMBLY.
14:04:22 Acquisition Test: FAILED
14:04:22 THE INTEGRATOR ZERO CAN NOT BE PROPERLY ADJUSTED (READS 1 ADC COUNTS WHEN SET TO
14:04:22 FULL ZERO). LIKELY CAUSES INCLUDE: 1) EITHER R20 OR R66 ARE MISADJUSTED ON THE
14:04:22 SAPWAVE BOARD OR 2) THE MANIFOLD ELECTRONICS ASSEMBLY IS DEFECTIVE
14:04:22 (ELECTROMETER) OR 3) THE SAPWAVE BOARD IS DEFECTIVE (INTEGRATOR/LPF).
14:04:22 Basic Heater Test: Passed
14:04:22 Ionization Test: Passed
14:04:22 Diagnostics: FAILED.
14:04:22 System Test: Completed
14:04:23 Diagnostics: Completed

When I tune the electron multiplier separately it comes out as:

Autotune- electron multiplier
12:13:48 Integrator Zero Set: Started
12:13:50 AveCounts: 4.00 (High) - CurAdjDAC: 128 - NextInc: -64
12:13:51 AveCounts: 2.44 (High) - CurAdjDAC: 64 - NextInc: -32
12:13:53 AveCounts: 1.93 (High) - CurAdjDAC: 32 - NextInc: -16
12:13:55 AveCounts: 1.10 (High) - CurAdjDAC: 16 - NextInc: -8
12:13:56 AveCounts: 1.00 (High) - CurAdjDAC: 8 - NextInc: -4
12:13:58 AveCounts: 1.00 (High) - CurAdjDAC: 4 - NextInc: -2
12:14:00 AveCounts: 1.00 (High) - CurAdjDAC: 2 - NextInc: -1
12:14:03 Integrator Zero Set: Setting is High (Setting: 1, Average Counts: 1.00)
12:14:03 Integrator Zero Set: Completed

In the diagnostics window for multiplier voltage I get:

Aquisition system multiplier voltage -2V in grey.

Not sure if this bit is relevant but the waveform reading is below:

waveform system axial modulation 4.1Vp-p

[erica]

Hello,

I had the technician to come and take a look at my problem. It was the integrator zero, and some adjustments needed to be performed at the SAP/WAVE board. For what you've shown, your problem seems to be the same; the integrator zero average counts should be around 0.5.
I tried to get this fixed by myself, but Varian/Agilent was very strict about this, they say only a trained technician should perform such repair. To be really honest with you, I watched the technician doing so, and it is nothing complicated, though.
I found some information in the web about this: http://gazanaliz.ru/books/Saturn_GC-MS_ ... ooting.pdf

Good luck,

Erica

[Ultimate Science 101]

Aoife,

As Eric suggested, there may be an issue with R20 or R66 on the sapwave board. If you attempt the adjustment, let us know how it goes. The multiplier should definitely not be reading -2V (is this the value it is reading when trying to achieve setpoint or when not in use?). There may also be a short in the manifold electronic assembly. Ensure especially the lower manifold board is making good contact with the metal housing and is properly grounded out. Your axial modulation value looks good.

[sideline]

Thanks very much for your replies! I'll have a go at the adjustment today and check the manifold board is connecting correctly as suggested. I'll let you know how it goes.

Aoife

[Hornet]

Hi, you can solve your problem for sometime like this:
-remove autosampler
-take off the top cover of MS
-take off the right cover of the ms, need to remove screws too (be careful there is high voltage), do not turn off the instrument.
-now on the right board (the sap/wave) find MX, it's an item with 3 plugs and an item that covers 2 plugs and you'll find it in the I position (don't remember if it's the upper or lower one) covering 2 of the 3 plugs. Take it off and put it in the L position, covering the central plug and the other one that before was free.
-on the item R66 there is a little screw, turn it while attempting an electron multiplier tune. Do little turns then try tune everytime (interrupt it after you get the integrator message) until you reach a setting of about 128, doesn't need to be exactly 128, but around it (125,135,140 for example).
It needs very little turning to move by a large setting.
-now move the MX back to the I position
-put on the covers-
-tune electron multiplier, probably the setting has changed a bit, it's fine

after this you can work, but keep on mind that your sap/wave board is probably defective and needs to be changed. If you never changed it you need to get a new one with an external bus that can be exchanged, they produced them after the instrument was out, original ones suck and need to be changed as an unique item.
If you have a new model just ask to change the bus.

The integrator zero will lose it's setting more often as the time passes, so if you have the money do a favour to yourself and get a new board, i was at the point i needed to set the zero everyday.

[sideline]

I did the adjustment- and it worked! Diagnositics passed no problem and the electron multiplier tune was fine. For a short time only though as now it says there axial modulation amplitude error (it reads 5.5). I tuned everything again but the axial modulation error showed up and diagnostics is failing again (saying waveform defective). Any suggestions for addressing the axial modulation problem?

Hornet- you are completely right about it being better just to get it changed. I'm based at a university though and they don't want to hear about us needing parts . Everything is breaking down in the lab at the moment so it's a bit of a nightmare. We are trying to fix what we can ourselves and prioritising what new parts are needed. I really need to run some samples but nothing doing while none of our GC's work!

Thanks to everyone for your help so far- would be great if you had any suggestions for the axial modulation bit.

[Hornet]

Good that it worked! Unfortunately there are big chances that your sap will get worse in the future, i assure you that a new sapboard with the external bus is a good investment. I changed mine 3 months ago, my old one was at a point that made me work with the instrument open for daily adjustment, it sucks.

[sideline]

Somehow the axial modulation came right again after another tune. Running standards just now. Thanks to everyone!

[Ultimate Science 101]

Glad to hear the integrator zero adjustment via the SapWave board went well.

The axial modulation is a small voltage (generally 3-5 volts) that is applied to the end cap electrodes only. It allows for better control of ion trapping within the mass analyzer. A larger voltage (around 180 volts) is applied to the middle (ring) electrode. If the axial modulation error comes back, ensure the trap assembly is properly assembled and the end cap electrodes are properly seated. Always check to ensure the lower manifold board is properly seated as well within the respective tabs holding it in place.