EM voltage goes to 0 HP5890 Series II/59709B MS

[jryter]

We have a lovely Hewlett Packard (Agilent) Gas Chromatograph 5890 Series II interfaced with a Mass Selective Detector, 5970B. We upgraded our computer and software for the instrument to WIN 7 through cssanalytical. Funny story there.... Anyway I don't know if this is related to that or just an old instrument problem but in checking out the system to make sure everything worked the EM voltage goes to 0 randomly in a run. Sometimes the run goes all the way, sometimes after 3 min or 8min it goes to 0 and flatlines. The vacuum is good, I can run an autotune, and no air/water leaks.. I get a reproducible peak when it runs that far. I was running a sample with just some caffiene in it. I tried it with nothing, no ramp on the program and with and it happens. I was goofing around with the mass range that is scans and it seemed to maybe work when I lowered it to 350 or so from 450. I'm not really sure there though.

advice on what boards/cables to check and diagnose. Anyone have all the old boards I could swap out?

I do have the fat book of schematics that came with the instrument but I'm sure someone has had this issue here!
Thanks
Jarral

[James_Ball]

Our last 5970 did something similar before we retired it. It would not stay with no signal like yours, but at random times it seemed the signal would drop very low then return to normal. It would begin by cutting out for a few seconds during a run, usually you would notice it if it actually happened when an internal standard or surrogate was eluting, otherwise you would have to look closely at the baseline to even find a hint it happened. After a few dozen injections it would become more frequent then it was like the detector was turning on and off repeatedly.

If you powered the instrument down and unplugged it for a while you could begin running samples again like normal then over time it would start doing it again. I think Agilent replaced ever board on the thing and never could fix it. I know that is not good news for your situation but we never did figure out what was happening to it. I hope yours is just a software glitch.

[jryter]

Actually I did see it go to zero very briefly once and then come back on. And it does seem to happen on 2nd, 3rd runs etc and not on 1st. Most of the time it stays off--or at least that is what I notice.

Actually if replacing all the boards on yours didn't help that may be good as then I can check cables first... Wishful thinking.... it is used in an undergraduate lab. We can't afford a newer one so gotta work it out. Maybe an instrumental chemistry project.. yeah real world activity.

[James_Ball]

Actually I did see it go to zero very briefly once and then come back on. And it does seem to happen on 2nd, 3rd runs etc and not on 1st. Most of the time it stays off--or at least that is what I notice.

Actually if replacing all the boards on yours didn't help that may be good as then I can check cables first... Wishful thinking.... it is used in an undergraduate lab. We can't afford a newer one so gotta work it out. Maybe an instrumental chemistry project.. yeah real world activity.

If you get a student to solve the problem, that would definitely give them a leg up on experience when going into a commercial lab setting or going to work for one of the instrument companies.