There is no emission current, HP 5971

[bjornbohman]

Wondering if anyone has any helpful suggestions to what could be the issue with my old HP GCD1800A i.e. 5971A GC/MS.

The problem is that more often than not the MS will not start but rather give error 8 / "there is no emission current". When scanning in tune window it takes several attempts to get it starting - often it requires fiddling with EM volts and repeller values. When it finally is scanning it all looks good. It won't start a tune either. I am running the very obsolete C1034 Chemstation coming with the 1800 configuration so can't tune manually but have to stay with autotune.

So far I have swapped the analyser with no change in results, and also the EM alone. The filaments are OK, and no different when switching from one to the other. Have triple checked all cables, connections etc. I have no means to check the high vacuum but always wait over night before testing, also changed the diffusion pump as the heater of the first one died while troubleshooting this problem... have plugged the transfer line too to rule out GC-related leaks.

Any suggestions are super welcome Thanks!

[Consumer Products Guy]

With our old 5971A that typically meant filament was burned out.

[rb6banjo]

Every time I've ever had a problem with getting emission current, it's been the filament(s).

[LCbob]

Hi
I have seen this problem on gcds. I usually clean the source which seems to remove the issue. Also blank off at the transfer line, my experience leads me to think this helps.
Never seen it on 5971 or 2s. Also its not your software as the ones i support are running on 1701ba. Let us know if your find a concrete solution please.

[bjornbohman]

Thanks guys, have cleaned the original source and the filaments are fine (the instrument does run once in a while in between error messages). During the weekend I have rebuilt the whole thing to a 5972, with main board, smart card, analyser and updated the software to 1701aa version where I can actually change settings etc. Still the same issue. The only thing in common now is the human factor (not the first time I've cleaned a source, but who knows what I have done this time ), so will ask a colleague to go through the analyser for me. What worries me is that I can't see the vacuum as I don't have a gauge so if there might be a small leak somewhere that causes issues. However, when I manage to get the scans going, it looks ok (m/z 18, 28, 44 all ok). Another clue, which I can't interpret, is that almost every time I manage to scan something, that is after I have narrowed the range from the preset m/z 10-425 to say 50-100 or so. Then I can broaden the range while scanning and it continues ok. Also, it normally starts scanning with calibration valve closed, but rarely while open (but again, after it started I can open the valved and it all works fine). Perhaps this will be of some help for someone. Will let you know if I manage to solve it!

[James_Ball]

It could be a pressure problem since I believe the 5971 did use a check on the draw on the filaments to check for bad vacuum. I remember that if a high solvent peak hit while the filaments were on it would shutdown the analyzer with a pressure warning. That is also why there is the switch on the front of the electronics cage for EI/CI operation, in CI mode it disables this feature. I had one that did similar things to yours and I just ran with the switch in CI mode and the problem went away.

I hope the switch is the easy fix, if not it could be in the main board or the power supply not sending enough current to the filaments. But since it seems to also be related to pressure as when the cal valve opens changing that switch may fix your problem.

Oh one other thing that I had happen on one, remove the top board and look at the ceramic pass through connector for all the source wires. I once had one what had weld spatters/burns between two of the filaments pins and once full current was applied it would short out. It can sometimes be fixed by sanding the area between the pins to remove the conducting material if present.

[bjornbohman]

Thanks guys, just to close the topic - problem seemed to be a combination of filaments and EM. With new filaments (although with same Ohm reading as the ones in there) the scanning started and with a new EM the signal is good enough as well. (So apparently EMs can go bad during storage, as tested a known good second hand one without any success, and the Ohm reading is not all there is to a good filament...)

[James_Ball]

Thanks guys, just to close the topic - problem seemed to be a combination of filaments and EM. With new filaments (although with same Ohm reading as the ones in there) the scanning started and with a new EM the signal is good enough as well. (So apparently EMs can go bad during storage, as tested a known good second hand one without any success, and the Ohm reading is not all there is to a good filament...)

The ohm reading on filaments is good to check for shorts or breaks but it can be misleading since it is done at a lower voltage and load than what they operate. We had one that would check out fine with a meter but would not fire, and found out it was conducting between pins on the ceramic passthrough under the top board. When they welded it into the analyzer plate at the factory there was some welding spatter between the pins and once you placed full voltage and current on the pins they would conduct and short out, but when checking with the ohm meter it was passing.

Also on EMs, unless you store them under vacuum they will degrade rather quickly. The only ones I have seen last very long at atmospheric pressure are the film type from ETP. When I ran my 5971, I used to keep a spare EM inside the vacuum chamber, just sitting on the bottom near the middle so it was away from any oil mist from the diffusion pump. It wasn't a new EM but a known good one that had been replaced and it worked in a pinch if the active one died suddenly.

[PaulFinch]

I have the same problem - intermittent NO EMISSION CURRENT - with 2 cleaned analysers and 2 5970MSD boxes; I have Pirani gauge at rotary pump and reckon vacuum OK (0.1 mbar).
Having read the posts am going to check connections BUT am only aware of 1 i.e. the flat connector with round cable on to the top of the analyser base.
Any other suggestions most welcome.
PF

[lgchrom]

Mind that 1034c and 1701 have different tune routines with the same name. Standard Spectra Autotune does a different thing on each software.

[PaulFinch]

On the last occasion after successful tune NO EMSSION CURRENT intruded during a blank GCMS run.
Since then switched to filament 2, no joy.
PF

[PaulFinch]

PS Have had to replace filament power supply fuse F8 from time to time
PF

[James_Ball]

I have the same problem - intermittent NO EMISSION CURRENT - with 2 cleaned analysers and 2 5970MSD boxes; I have Pirani gauge at rotary pump and reckon vacuum OK (0.1 mbar).
Having read the posts am going to check connections BUT am only aware of 1 i.e. the flat connector with round cable on to the top of the analyser base.
Any other suggestions most welcome.
PF

5970 is a whole different beast versus the 5971/72.

Have you ohmed the filaments to make sure there are no shorts inside the vacuum chamber? It has been at least 12 years since I used one and someone here threw out the manuals I was hanging on to(curse those anti pack rat people). If I remember, those filaments sometimes had to be repositioned with some forceps to make sure they don't ground themselves when you reinstall the source onto the analyzer end. There was an assembly block that held the ceramic piece and other parts while you put the filaments on that allowed you to make sure they would align properly with the tiny slot cut in the ion chamber. Also the T shaped ion target that slides down beside the filament can touch it and ground it out and keep it from working if you are not careful when reinstalling it.

Those sources were a pain to clean and reassemble but man I wish they still made those units, they were the most stable I ever used.