Lamps get noisy as they age. Could be time for a new lamp. Could also be time to replace other components. Usually, you go from the lamp and work your way toward the photomultiplier (window, mirrors, grating) - just follow the light path and replace things one at a time until you have a good signal and low noise.
Amp boards also get noisy but this usually looks different from old lamp and crazed optics noise.
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Amp boards also get noisy but this usually looks different from old lamp and crazed optics noise.