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Why would two SCD 355 detectors have such high signal outputs?

Question asked by glapointe on Mar 7, 2018
Latest reply on Mar 19, 2018 by james_jenkins

We have three Sulfur SCDs, two of which have inordinately high signal outputs:

        1) Agilent 355; Model #G6644A; SN #CN11411006; PMT #DC7303; with FID on HP 5890 Series B

        2) Sievers 355; Model SCD355; SN #0500-918; PMT #WB5942; with FID on HP 5890 Series B

On 1), after starting up for the 1st time in many months, it's signal output pegged at 1270 mV for both Attenuation 1 and 100

After a day, the signal came down to below 400 at Attenuation 100, but the noise fluctuates between 100 and 400 mV

O3 generation, on or off, doesn't appear to affect the noise.

Shutdown plugged the detector where the transfer line comes out, restarted, and still had the same thing.

On 2), after starting up for the 1st time in many months, it's signal output is pegged at 120 for both Attenuation 1 and 100

It has been running for about 5 hours, the output seen on EZChrome is 11145 mv

By the way - the 3rd SCD has been working fine after starting it up, and we successfully have been running standards & samples

Why would the first two SCD 355 detectors have such high signal outputs?

What can we try, to troubleshoot, or better yet, to do, in order to solve this problem?

     Thank you,

           Gino

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