Beckman DU640 zero order

I just acquired at DU-640 with the ZERO ORDER calibration error.  I also fixed the mouse issue by soldering in the jumper, removed the bumper goo from the circuit board, replaced the battery, cleaned one of the fogged filter wheel filters,  I replaced the UV and Visible lamps, and peaked them.  At 0nm, the white light slit is over the exit slit and measures 14.38 V at TP1.  The instrument passes all the self tests, and even (barely) passes the performance tests.  The wavelength is off by 0.5-0.6 nm. It also passes calibration cuvettes.  However, I would like to perform the wavelength calibration to get closer to the expected value.  I also checked the beam path using the microcuvette holder while at 0nm and it looks good.  Can anyone give some insight as to why I am still getting the zero order error?  I checked calibration factors.  The only thing that stands out is the D2 reference location = 0.  I am not sure what this means, but in a DU-800 manual, it shows a different non-zero value for D2.

Thanks for any help,

Clay

I too have a DU-640 that returns a zero order error on wavelength calibration. All start-up diagnostic items are passed. Scanning an empty path from 600 nm to 700 nm (after blanking) puts the deuterium 656.1 nm peak at 650.0 nm. What is the precise meaning of Error: Zero Order? Can anyone provide advice on how to correct the shift in the measurement of the deuterium peak? Thank you.