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Beckman DU-650 won't cal wavelength
re: Beckman DU-650 UV-Vis spectrophotometer
After running the built in wavelength cal function, it fails. It seems to function fine except for this. Using other standards, it appears the wavelength is off by 5 or 6 nm. Is there some secret code I can shift the range to where it expects? Or anyone have a service manual so I can make an adjustment?
Let me have the Serial Number for the device and your location, I may be able to give you exact instruvtions.
Let me have the Serial Number for the device and your location, I may be able to give you exact instructions.
The DU-650 is sn 4321024. I am located in Rochester NY.
I had the same problem. Open the case and observe the start-up procedure. Just make sure you do not look at the UV lamp. The filter wheel flicks through a range of filters to do the tests. One or more of the filters will be dirty or damaged and the test fails. Also check the UV lamp hours. It needs sufficient UV power to run the tests. Run a baseline blank then scan across the spectrum. It should be smooth. If there are jumps and jagged absorbance then the filters are probably at fault. There is a service manual I bought for lots of $ but this was content free. I do not know how to adjust to get the right peaks but I would start with the filters. If there are right then it should be calibrated in the right places. If the optics are dirty then this should be fixed. Good luck.
SInce my previous problem I have had something worse come about. If I do a full range scan (200-1100nm), scan a baseline, then scan with a clear piece of glass in the sample area; I get a scan that flat tops a small bit over 100%T but just in the region on about 500 to 1050nm. Out side this region things are pretty normal. It seems like it is not applying the baseline to this region, or is getting way too much energy.
I had the thing apart and found the following;
1) The rubber bumpers used to keep the daughter boards (which plug into the maion circuit board) from being able to press all the way down to the main board; had turned to liquid goo (like the feet of old HP equipment) This good had flowed several inches onto the circuit board and under IC's. I cleaned as much as I could get off with alcohol .
2) The mirrors all look remarkably clean. One filter on the filter wheel (purple) has irregular "frosting" on one side which would not clean off with alcohol. This is probably my previous problem of not seeing the UV peaks to be able to calibrate wavelength.
After re-asssembly I still have the same problem. I am thinking my mainboard has failed.
Question: where can I purchase a mainboard (preferably used and reasonable) and are filters available for the filter wheel?
I think I answered my own question! In diagnostics I ran "setscangain". The Baseline flatness, which was less than 0.002A, and less than 0.0005A from ~vis to 900nm. Doing a wavelength scan now works!!
This makes sense since all along I could use REadiread or Fixed Wavelength read at any wavelength and get reasonable results. I am not 100% sure, but I think that I tried setscangain in the past but it did not help.... maybe cleaning the board and connections?
BTW; for those of you fixing these things; I also noticed that the 3 mounting bolts which hold the optical chassis in place to the main baseplate were much longer than needed and protruded from the bottom so they were longer than the feet. I shortened them up by adding a nut to each screw.
Anyway, I still could use a filter or filter wheel to fix the rest of my problem; anybody have a source?