high source temperature

[Spectro]

Help, help,
I opened and cleaned the sources of my MSD. However, the source temperature reached up to 561 degree, really high. The vacuum could not turn on. I did not know what I did wrong. I remember I turned the pump down before tuning on the source.
Please advice. Thanks all, Spectro.

[bhuvfe]

Probably you have a broken sensor or some of its wires are not making contact with the electronic board. If you have a Agilent system (GC-MS) it can happen sometimes after source cleaning.

[Teodor]

What do you mean by "turning the pump down"? You should not turn off the pump while the MS is turned on in order for the pressure inside the analizer chamber to drop to a apropriate level. Also, on the mass spectrometers I am familiar to (Thermo), you set a specific source temperature - for eg. 250C - and all the tuning process gets done at that temperature. So, it would be very helpful if you post your instrument manufacturer and model.

[Ron]

One of the leads to the RTD sensor on the source is probably broken or shorted out. I not sure since it has been quite a while since I had to deal with this, but it seem like a broken lead will cause a maximum temperature reading and a shorted lead will cause a minimum temperature reading. I may have them reversed, but an extreme temperature reading is caused by either a damaged sensor or a bad board.

I'm assuming you have an HP MSD with a temperature sensor close to the source assembly. The sensor has to be handled very carefully, the leads are very thin and easily broken if they are bent repeatedly.

[Omaejel]

I have seen many problems as of late with those little temperature sensors on the 5973's and 5975's. I think our analysts have been handling them pretty roughly when they clean the MSD.

When you have a broken lead it will not read a temperature at all. I guess the shorted lead must be the one that causes the higher reading. The MSD will not pump down when this error occurs.

Has anyone tried to repair these wires when they break? Those sensors are around $300 if I am not mistaken.

[Ron]

It is not really practical to reweld, often the break is right where the lead enters the ceramic body. To reweld the lead you need a small high temperature torch, and you run a big risk of damaging something else. I have welded platinum in the past, and it takes some practice to get a good weld.