GC-MS - filaments relay

[Roxanne42]

Hi there,

Our instrument is perhaps a year old and hasn't gotten an extreme amount of use in that year. We have an Agilent GC-MS (6890/5975). Our EI source has two filaments (which can be selected from the software).

We had only used the first filament so far when last week we came across the problem where the filament just wouldn't light up. You'd hear a "click" as if voltage was been sent but it just wouldn't light up. Switching filament with the software didn't help either.

Thanks to a knowledgeable co-worker, armed with a voltmeter, we were able to test the the filaments, cables, fuses, etc. Everything seemed normal at that point, which was rather confusing. So we went deeper and started testing the power path to the filaments on the board. This is when he discovered that power appeared to go to BOTH filaments. This is to say that the relay box on the board appeared to be malfunctioning and the voltage was split and sent to both (parallel) wires at once, which in essence was not enough voltage to any of the two filaments.

The theory was verified (and the problem resolved) by removing the second filament and installing a dummy in its place.

Anyone run into this type of problem before...? Was curious as to what caused it. We typically keep the source at a temperature of 230 degC and the MS quad at a temperature of 230 degC (even in standby mode).


Thanks,

Roxanne.

[Rick]

Hello
The "clic" you hear is not produce by the filament opening. The clic is produce when the calibration valve open.
I have not this problem....Sometime, the calib valve don't want to open.
A good pratice to verify the filament is to check profile in Edit tune parameters section.
If filament is o.k., you will have a signal.
With the window on the new 5975, you can see the source.

[jaj]

Roxanne,

I believe that you must be speaking of the ion gauge tube and not the filaments. One cannot see the mass spec filaments "light up". Unless of course you are speaking of the filaments inside the vacuum gauge tube.
What does your software say the vacuum is? If you can scan and have peaks, then you do not have a problem with your mass spec filaments.

[Roxanne42]

No, the filaments are definitely fine. It's the relay box (the "switch" essentially) that sends power to one or the other. It not appears to send power down BOTH paths. Which is why if the circuit is complete in parallel, it doesn't work. But by taking out one of the filaments, the problem is resolved.

I was mostly wondering if anyone had come across this and what could have caused the failure of the relay box on the top board.