Chromatography Forum

Hi.
I've had problems for a while with auto-tuning, and the instrument has been unable to perform detector gain calibration. I have repeatedly cleaned the ion source, lens assembly, prefilter etc, and also replaced the electron multiplier (temporarily fixed the problem for ~1 month), topped up calibration gas vial, and replaced the filament. Apart from this issue the GC-MS has been working fine. No faults were previously detected with the diagnostic tests, but yesterday it failed on lens diagnostics. Lens 3 appears to be the issue. It does not show a flat line response, but instead starts off flat and then ramps linearly before leveling off again. I cleaned the lenses, but this had no effect - apart from the auto-tune (inc. detector gain calibration) now seems to work OK for the first time in 3 months!! The troubleshooting section of the DSQ manual suggests that the analog PCB or regulator PCB in the power module may need replacement. Question is how do I know which (if either!) is causing the lens problem? I'd be really grateful for any suggestions.....

If you disconnect the big white connector on the Analog PCB going to the Source Interface PCB and then rerun the test you can get an idea..

If the test still fails it is the analog PCB. If it now passes the Analog PCB is clear and it is further up the stream.. you could then disconnect the connection inside the manifold going out to the Source interface PCB and run the check agian.. If it now passes it is in the source region.

But as you will be running the instrument live and opened up please be careful! Set the electronics switch to service before unplugging or reconnecting a connection.

Thanks leadazide. I've just tried your suggestion and it seems that the Analog PCB is the issue. I'll look into replacing it.

If this is an old DSQ classic you might want to think about if it is worth getting it fixed.. the pcb is expensive!

Maybe you can get a good trade in value for a newer gcms instead..

Unfortunately, we don't have any budget for repairs let alone a replacement GC-MS at the moment. The analog PCB was replaced in 2010, so it is a bit frustrating that it has only lasted 3.5 years. I'm considering trying to get the PCB repaired - I don't know whether it is possible, but it is perhaps worth looking into..

Thanks for your help.

The ability to fix boards requires specialist knowledge and alternatives to service by Thermo can greatly reduce the cost of an engineer visit. There is not even Country info. about you so no point us posting alternate solutions

Sorry - I'm UK based (West Sussex).

UK based , you have access to a wealth of third party experts , many of whom built the systems in the first place. My "favourites" are Mass Spec Technologies
http://massspectech.com/ they used to build Thermo's MS systems. They can certainly help at a lower cost than Thermo direct.