Agilent MWD / DAD noise test fail UV and Vis

[Emefede]

Hello everyone,

I have an Agilent MWD G1365A detector that's noisy. I ran the Quick Noise Test with the LabAdvisor. I removed the cell and got 2.409 mAU of noise at 254 nm and 0.130 mAU at 750 nm. I have a G1315A DAD near, and if I insert both MWD lamps, it passes the test, so it's not a lamp issue. It seems like the problem is electronic, right?
Would updating the firmware help?
Any suggestions?

Thanks and best regards!

[scottythree]

There are three cell windows (lenses) in the path from the lamps to the detector: Coupling Lens Assembly, Source Lens (Achromat) Assembly and Cell Support Assembly. I do not replace the coupling lens assembly one as it lies between the two lamps and I do not run Vis wavelengths. I have had great success swapping out the Spectro window P/N: 79880-28111 in the other two assemblies for noise issues when I determined the lamps and flow cell are good. These Spectro windows/lenses develop what looks to me a white colored film/burn on them over time. This swap out has fixed my noise issues on 19 of 20 DAD and MWD's over the years when new lamps and flow cell still failed for noise. The one time it still failed after swapping these I swapped out the entire optics bench from a parts system and then that solved my noise issue.

Caution to do these swaps you need to pull the optics bench out, pull off the Holmium filter holder (can be a pain in itself), pull the assemblies out (can be a pain) and then disassemble the cell assemblies (can be another pain) then put it all back together. You probably could purchase the entire cell assemblies for much more $$$. I got this procedure from an old 1100 DAD/MWD detector manual, back in the day. Agilent took this procedure out from newer versions of the 1100 and 1200 manuals I presume because people were totally breaking their detectors trying to do it. I haven't had a noise issue on my 1260 detectors yet so I never dived in to see if it is a similar design. I do not have the manual anymore, I just learned how to do it back in the day.

[Emefede]

Hello, thank you very much for such a detailed explanation. I replaced the entire optical bank with one from a DAD that passed the noise test, but the noise persists in the MWD. ​​Therefore, the problem is in the motherboard electronics. The motherboard must have become "old" due to some capacitors, as I read somewhere, and that's the source of the noise. It seems I'll have to replace the motherboard. Thanks and best regards!