Problem fixed.
*Phew!*
Reseating the connector on the mother board near the GPIB port did the trick. I thought I had reseated every connector in the machine, but I had missed that one. Time and connection corrosion takes its toll. I'm assuming no power was getting to the PMT amps. (Over the years I've removed and reseated every connector and socketed chip in this beast, several times. Routine maintenence, it seems.) It's working flawlessly, again.
Cheated death one more time.
I've scanned the USAF target and get slightly better than 4096 dpi resolution RGB or monochrome. That's the design point of the machine, so its optics are performing as intended. I don't know how much LCA may be present in the lens (very little I assume), but trying to improve it won't do anything to better the scan resolution of this particular specimen.
Much thanks to Andy and Armondo for help and encouragement.
Rich
I have been looking for a good drum scanner for quite a while. I just picked up a Crosfield Celsis 240 (Howtek 4500) for $50 (part of an auction lot). It powers on, I can move the carriage, focus, bulbs work, everything so far looks good and the readout says "Ready To Scan" with the latest firmware. I need a Drum, Mounting Station, and a SCSI card (and supplies) to begin scanning. I'm currently running 5 computers in my server rack (I also do video production, editing, photography, sound...) There are some modern i7 Win7 64 Bit machines (2 with PCI-E slots only, 1 with PCI slots as well) and and some older P4 WinXP 32 Bit machines with PCI Slots.
Any recommendations where to pick up a mounting station and a drum (I tried Aztek and they're still in the pre-manufacturing stage) would be much appreciated! Even an older drum that I can use to test the machine would be helpful.
Thanks!
-Jeremy
I'm in Toronto, Canada btw.
You are better off using a winXP dedicated machine. You can easily find SCSI cards that work in XP machines fairly cheap in EBay with cables.Mounting stations for Howtek 4500 occasionally come for sale in Ebay again. All the supplies you can buy from Scanscience a Canadian company. Your main problem is going to be finding a drum. I found it almost impossible to buy one. The sellers usually sell their drums with the machines. very expensive also.good luck
An update regarding the optical system tests.
Spent some time improving the alignment of the optics and no sign of improvement in the results.
Then I decided to check the coherence. It seems the level of coherence in the light source is the a big source for the chromatic aberrations observed. You can test it introducing some diffusion in the light source. For D4000 or D4500 owners, pull the GG glass out the viewport and place it in front of the lamp and scan the target. The results should show very little chromatic aberration. It was driving me crazy.
A lot to read and test.
Hmmm. That's an easy enough "optical element" to add. Or maybe just fine sand the end of the FO bundle with 400 grit?
I'll try that (ground glass diffuser) in my scanner and see if I still get the CA Andy was able to uncover in my file. Although, as I've said, I just can't see its contribution in actual scans.
Rich
Here's a simple tool to check the internal alignment. Just get a small cross-point laser pointing inwards replacing the lens.
It should be checked to ensure, between other things, the aperture gets the best of the lens. The regular alignment tool only centers (and some models focus) the illuminator.
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Quick note about the apertures. The aperture wheels holes are not 3, 6, etc. microns in diameter. They are in fact around 30, 60, etc. microns because the main lens introduces around 10X magnification. Selecting the aperture size is important because it defines the real optical resolution, regardless of the sampling. For example, if scanning at 4000 dpi with an aperture of 13 the optical resolution is limited to 2000 dpi. If scanning at 8000 dpi with an aperture of 6 the optical resolution is limited to 4000 dpi. No way around it.
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