G1362A RID Diode Balance. -1 or 1

Hello, while trying to balance the diodes in our RID we discovered that no matter how small of an adjustment is made the signal will only vary from -1 to 1.  The detector has been purged for hours with water and mobile phases and appears to be free of any air bubbles.  My thoughts are that one of the light receiving diodes has become faulty thus making balance impossible.  Any help would be greatly appreciated.  

  • Just to clarify: You are pumping water at 1ml/min and you switch the purge valve to the ON position. You keep pumping for about 5 mins and while still pumping, you switch the purge valve to OFF. You repeat this 2-3 times and then you should have a thouroughly flushed system. While displaying the diode balance (are you using LabAdvisor?), you carefully turn the set screw until you see 0.000.

  • I just wanted to make sure you understood how to use the purge valve to flush the system and use the set screw. Some people don't understand the working principle.

     

    Your guess one diode is faulty could be right, but also the main board could be defective, but less likely. I would ask for an Instrument Exchange module at a fixed price or, alternatively have the repair done with an exchange optical unit (-69 part), which is less expensive.

  • No, there are no additional tests for the diodes or the optical unit itself. If the diode balance cannot be achieved with a well flushed system, something is broken. As mentioned, repair level would be either the optical unit or the main board. Usually they don´t break, but it depends on the age of the RID. More often the purge valve goes bad (mainly by leaving it sitting in water or buffer) and then you would also have issues with the diode balance, but at least you could see moving readings, not just 1 and -1.

  • I appreciate your help, and we are discussing repair options now.  Would there be any type of diagnostic test that I could perform on the module to narrow down the root cause?  As of now, nothing can be run on our system before the error message clears on the RI module.

     

    Thanks again.

  • Here's what we have on tests in LabAdvisor:

     

    You could possibly look at the individual diode readings either in LabAdvisor or in OpenLab, but in your case it would only be a graphical interpretation of your 1/-1 readings.

  • Hello !

    have you solved your problem? Can you tell us what was the reason and how you solved it? The fact is that I have a similar situation. But I think I have a problem with the quartz cuvette. I believe that the people who worked on this detector exceeded the PH level of more than 9.5 and the cuvette deteriorated.

  • Azrael, honestly, it could be any kind of contamination or damage in/on the cell. Of course, if someone lets the system sit in NaOH or something similar, the cell will suffer.

    As mentioned earlier: It's vital to thoroughly flush both sides of the cell with water and then with IPA (obviously not with water, if normal phase was done before) when the RID is not in use or even gets stored for a longer period of time.

  • how can i check a cell? Has it deteriorated or not?

  • The repair level is the entire optical unit. You cannot check or replace the cell individually. That's the same for almost all RIDs on the market.

  • what if the photodiodes are broken? Are they also related to the optical unit?

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