5973 Source Heater problem

[verge]

Hi, I'm running a 6890 w/ a 5973 MS attached. I've worked on similar systems in the past; this one is a recent acquisition. I'm trying to get it up and running to validate a P&T GC-MS method for VOC's. Prior to doing the actual method development work though, I've run into a problem with the source heater.

After pump down, when the source and quad heater temperatures are moving to the setpoints, the source heater reading was highly volatile, ranging from ~180 to ~520. Chasing the error numbers in Chemstation lead to the diagnosis of 'Source RTD not connected'. The quad temperature readback varied slightly, but not as extremely.

I should mention that after the first error, I pulled the source and cleaned it and made sure the connections were from the heater to the board were solid. No improvement was found on pumpdown.

Not wanting to spring for a full source heater assembley from Agilent, I ordered just the source temperature sensor from sisweb (the sensor shown here: http://www.sisweb.com/ms/hp/5973heater-sensor.htm). That arrived today. It pumps down now and the performance is better in that I'm not getting any error messages.

I am worried that this was a bandaid at best. The source temperature now fluctuates ±10 C from the setpoint. Example - setpoint 230, heats to ~240, then cools to ~220, heats to ~240 ad nasuem. The quad temperature is rock solid at its setpoint.

The question now is whether or not this 20 degree fluctuation is likely to cause analytical difficulties going forward. Any suggestions on the next step?

Thanks for your time,

Kent

[verge]

To answer my own question, yes, it's a problem to have that much variation in the source temp. Won't even pass a tune.

Any comments still appreciated.

[Rick]

The temperature variation is not normal.
It's probably a bad contact.
I suspect a bad contact on the small ceramic piece into the MSD chamber where ion source heater ect is plug....
Clean it with contact cleaner and isopropanol
The dirt is habitually on the back of this ceramic, so you need to remove it from the side plate...."carefully"

Rick

[Omaejel]

I have seen this 10-20 degree fluctuation in temperature on more than one occasion in different instruments. It could possibly be the actual heater element. I have replaced these before and seen this problem go away.

If you see the temperature change drastically (like it was initially) it is generally the temperature sensor, but I have seen a few occasions in which the feed through board (the ceramic board on the inside of the analyzer chamber in which the heater wires plug into) has a broken solder joint. This will cause some weird things to happen. I would pull that board off and check all of the connections with a multimeter. Make sure that whatever plugs into it on one side has a connection on the other side where it plugs into the pins sticking out of the side plate.

Once I had one of these boards that took me FOREVER to find the broken solder joint. I finally found it by wiggling the post the temperature sensor hooks to and noticed that when I wiggled it, contact was broken. I have had to re-solder a few of these and they are still working in my lab right now. I guess over time they get some stress to the joint as people plug them in and unplug them when sources get cleaned.

So there's a few possible causes. I hope it helps.

[verge]

Thanks for the replies. I'm still having the problem with the temperature fluctuating ±10-15 degrees from the set point. It doesn't seem to be having too much of an impact on the performance of the instrument. If I override the stability warning, I can tune and my calibration curves are passing quality control. (Previous failure to tune was unrelated mistake on my part)

I vented it today and checked the connections at the ceramic board and on the pass-throughs - everything appears to be fine and there is no 'wiggle' to either of the posts.

Does anyone know if the quad sensor/heaters are the same as those on the source? They look physically identical except for the length of the leads. Could I swap the heater from the quad to the sensor to see if the instability moves with the heater and thus narrow the problem down further?

Thanks again for the help.

[Ultimate Science 101]

Kent, you should check with SIS. I'm guessing you received a faulty RTD. They changed their design about two weeks ago and incorporated a different spring to ensure the RTD makes better contact with the ion source block. A replacement RTD will likely resolve your problem. Good luck!