Chromatography Forum

Hi everyone,

i've read this forum for quite a while and sadly this is now my first time I have to write here and it is because of a little problem. I am working on a Trace-DSQ system and it is usually running fine. But every second day the RF dip and therefore RF gain and the Rod DC will freak out and give me faulty readbacks. While my machine freaks out of course the system won't work because of the non working RF dip and Rod DCs. And while i was already trying to find the argument for my boss to replace it....suddenly the problem dissapeared again. I am a bit baffled since i have no control over the problem or can influence it. I need some kind of advice what to do next, should i adjust Rf null? Or is it because of a wrong placed ion volume( someone told me they are a bit tricky at the DSQ, got the interlock option).

Thx for your help in advance

Hey guys,

small update on the matter. The RF dip calibration and adjustment finally worked and even not beeing perfect (Setpoint 1096,7; Actual: 1096,6) it is stable now for more than 24 hours. The Rod DC test passes most of the time and when it differs it is just small abbreviations from the set points, not like before with -500V and +500 V. When the setpoint is 50 it is now almost always 51 and 49, just had it once in the last 24 hours that the machine made 61 and 37 V.

What did i change? Nothing really just dusted of the Quad and the PCBs a bit. Sometimes this whole thing seems like pure magic to me

Since the old ion volume gave me just a gigantic peak from 30-200 (really broad and award with some ripples in between, indicating its more than one thing, i changed the ion volume and even passing every test i can't get a clear air/water spectra (meaning more precise no peaks at all).

I am now suspecting the positioning of the ion volume beeing the problem since i don't see any peaks. I'm extremely glad i got the vacuum interlock option and fiddling around with that is possible without venting every time.

But i am still looking forwards for tips and ideas to bring the old DSQ back to its original performance

I d not know your specific instrument but in general huge and erratic jumps like you were seeing are caused by poor electrical connections - which might arise from displaced components. These problems frequently vanish when you do TAR-A (take apart re-assemble) as appears to have happened to you.

Peter

That seems to have been the problem with the Rf calibration you are right. Thx a lot, now i have to find out why i don't see any peaks (neither Air/Water/Helium or FC-43)....

Permanent drastic problems like your lack of peaks can be due to a complete absence of a connection ! But then I would expect some self tests or the tune to fail dismally (I'm assuming that you have run a tune). Check that you have carrier gas flowing.

Peter

TAR-A really seems to have done the trick. As i noticed today that the peaks are visible again (4,16,18,28 etc.) maybe small leak because 28 is higher than it should be but it seems to be working right now. Beeing totally happy i noticed that after raising the source temperature the peaks started to vanish again and just flickering came up. I deactivated the transfer line and cooled the ion source down to 150°C and voila the peaks came back. Transferline(set to 250°C) and ion source i kept at 150°C and the peaks are still present. I just started a test run to see if a run can be made under this conditions, even i wouldn't like that very much since a 150°C source should mean i have to clean the ion volume even more often than before.

But everyday something new, would get boring if I it is stuck at some point

Beeing totally happy i noticed that after raising the source temperature the peaks started to vanish again and just flickering came up. I deactivated the transfer line and cooled the ion source down to 150°C and voila the peaks came back.

Have you checked the filament is still on? (Should be an obvious white light) If you turn the filament off (But instrument still in operate) do you see any emission current?

I often use a TSQ to do CI (Presume the source is very similar) When the little circuit board in the source gets dirty, I can turn the filament off, but the readbacks still indicate emission current is present. (voltages are leaking through the dirt)

Try turning up the emission current up and see if the peak comes back. If it does then clean/replace the little circuit board.

Hey Filament is on for sure, thx for the input.

But lately the Rf Dip problems occurs again. The Rf dip will get a plateau on the bottom and in general it looks more like \_/ instead of !/ really weird therefore the Rod DC will get a wrong result. Going to call thermo on monday

So still basically stuck at the point where the Rf system seems to malfunction or is wrongly adjusted. The Rf DIP won't adjust properly since at -10V over a long range of frequency the system saturates therefore the _/ instead a smooth I/ dip.... damn thats annoying

So i had a nice talk with Thermo and they send me new boards (Rf Generator and DC Driver) but the problem persists so it is definitely not caused by those two boards. They didn't really seem to have experienced that problem before
Sadly i cant upload a diagnostic screenshot to show you guys the problem. Since no one could help me to this point now, i will be forced to take my good old DSQ to the service (company is just 140 km away from me)....Too much invested to throw it away because of that (250l/s turbo, CI Upgrade, Vacuum interlock upgrade) i have to spend the money to get it fixed again.....would have been nice if someone could have helped and fixed it easy. I keep you posted what the problem is so the next one doesn't have to spend a lot of money for service.

Thomas

It could be your electrical supply that initiates this problem. Insert a surge protector between the electrical outlet and the instrument(s). They are inexpensive (cheap)!

Tomorrow i'll bring the DSQ into service and on wednesday i should know what the problem was. I'll tell you all immediately.....hopefully my DSQ will run and be my working horse again.

So maybe too late as you already shipped system in for repair but I have previously has really weird RF issues on a DSQ due to the two magnets in the source where not set correctly. It is crucial that they face the same way so they generate a uniform field thought the ionaization area.. So Pos/neg in the same direction on both and not pos/pos or neg/neg pointing towards each other.. I don't recall if the actual orientation of the magnetic field is important but it has to be "flowing" the same direction..

Be careful when manipulating these magnets.. they are really strong and very brittle so when remounting them they have a tendense to SNAP on really hard and shatter or parts break off.. and this can cause regular fields..

Also playing with the positioning of the magnets in the slots (all the way forward or all the way back) can change intensities a good amount so worth trying also..

Got my system back today. It was a faulty Rf-Detector board that caused the trouble, replacing it was around 1,5k but now its running smooth again. So like a baby, just happy it is healthy again