Waters 996 PDA Troubleshooting

[khykes]

Hi There,

Having some issues getting a used waters 996 PDA up and running. When running diagnostics I have a shutter failure, lamp failure, wavelength error and an optic test failure. I tried to deal with the wavelength error by running the PDA calibration process, but I find the process takes a really long time and had to end the run after about 40 minutes before it even completed. Is this normal and if so I should just let it run its course for however long it takes? As for the other issues, I plan to clean the flow cell before I venture into replacing the lamp. However, any feeback/advice on this topic would be very appreciated!

[uzman]

Shutter failure may cause the other stated failures since no light can reach the detector.

[HbJ]

Do you hear that distinct *snap*... *snap* *snap* during the boot-up of the unit? That's the shutter operating.

[khykes]

Do you hear that distinct *snap*... *snap* *snap* during the boot-up of the unit? That's the shutter operating.

I hear snapping noises but not specifically in that order. It makes me hopeful that the shutter is working, but I am not finding to many online resources for how to inspect or troubleshoot that specific piece.

[khykes]

Today I decided to try and clean the flow cell as I am sure that hasn't been done in a long time. I was following the procedure in the Waters 996PDA Operators Guide, but the first problem I ran into was that when I loosen the three screws holding everything in place I cannot "gently" slide out the flow cell. In fact, it doesn't budge at all. Has anyone else encountered this issue??

[HbJ]

I have *two* screws on my flowcell.

Please post a picture of what *three* screws you did loose up.

The mounting of the flow cell is depended on the in- and outcoming stainless steel capillaries. If those are bend, fitting the cell can be quite a pain. The easiest way to remove the cell is:
1. Loosen up the two mounting screws
2. Remove the front cover
3. Stick a broad blade (over 3 cm at least) from above between the cell and the mounting to push it forward.

You can check if the flowcell is jammed by looking at the two screws under the round handle. If they are just evenly exposed a bit the mounting is okay. Anything else hints towards improper mounting.

But before you do all that please check your lamp spectrum within the PDA calibration screen (Clicking on "RUN"). Does it show a spectrum and does it change when you operate the shutter (checkbox "DARK")?

[odbest2]

I wonder how the OP got on with solving this issue as I'm having the exact same problem in that the shutter error means the status light is constantly blinking. I have removed the flow cell and cleaned it but the status light is still blinking (please see diagnostic report below). The only thing I did not do while cleaning the flow cell unit is change the gaskets as we don't currently have spares.
I was wondering if someone would be able to help me, if I replace the gaskets with new ones will this solve the problem or is there something else that I am overlooking here?
I have already changed the lamp by the way.



Thanks

[HbJ]

Please open the "PDA calibration" and click on the "Run" button. You should see the spectrum of the D2-lamp.

But from the diagnostics output (especially the "GD!" from the optics bench) I suspect a dead charge amplifier board (the exact same happened to me some weeks ago) in the optical bench.

I'm trying to diagnose that failure mode at the moment.

[odbest2]

Thanks for your response. I have tried this many times and even after leaving it for several hours the image below is what I get



I wonder if this is the cause of the problem? In the meantime I've ordered a new lens assembly and flow cell gasket to rebuild the flow cell unit.

[HbJ]

Your detector has an electronic fault in the amplifier board of the optical bench. The detector cannot process the light coming through the flowcell as it's basically blind (the diode array resides on the amplifier board itself).

Therefore, your rebuild of the flow cell will be in vain.

[odbest2]

OK. Do you know if this fault can be rectified and if there is a replacement part?

Thanks

[HbJ]

I've yet been unable to find the fault on the amplifier board.

So please contact a service company (in Germany I'd recommend Fischer Analytics) to sell you a "Charge amplifier board".

It's located on the left side of the optical bench with the flow cell facing you.

The steps for changing it should be:

- Take off the cover of your 996.
- Remove the ribbon cable as well as the small coax cable (it's a screw-type connector so you need to unscrew it before removing the cable) on the optical bench.
- Unscrew the cover of the charge amplifier board (it's where those two cables on the optical bench go).
- Remove all screws holding the charge amplifier board in place.
- Mount the replacement charge amplifier. Be extremely(!) careful with the diode array as it gets easy contaminated or damaged!

As you've just changed the diode array itself the optical calibration of the unit is lost.
You need to fix that in order to get any meaningful results.

I recommend the following procedure:
- Connect the ribbon cable and the coax cable to the charge amplifier board after you've mounted it. Don't screw it in too tightly yet!
- Now fire up PDA calibration and check the alignment of the D2 lines. They shouldn't be more than 5nm out of calibration. You can correct major deviations by wiggling the board ever so slightly to the left or right. Please be careful though: The board is life and you or the board might take permanent damage.
- Do PDA calibration.
- Let the detector run for an hour and recheck the calibration.
- Now switch off the detector and screw in the detector board firmly but don't overdo it. The diode array doesn't take torsion too well.
- Remove the two cables, remount the cover and reapply the cables as fit.

Depending on how brave you are (exposed circuit boards!), you can run a standard like caffeine before applying the cover of the amplifier in order to see if the spectra match.