We have a Model 485 Spectroscope

iFixit may be able to assist with the Model 485 spectroscope if the issue involves a repairable component, but calibration and obsolete-part replacement may require specialized support. I suggest contacting iFixit with the model number, fault details, and a few photographs to confirm whether they can service it. You may also contact the original manufacturer or a specialist in optical instrument repair for alternative parts and calibration options.