Here's an update on my scanner woes.
I sent my second FS4000US scanner to Canon for repairs. After three weeks Canon tells me there is nothing wrong with the scanner. They cannot duplicate any of the problems I have been experienceing (see earlier posts). I sent them hard copy examples of red streaks and dark noise. I sent them numerous references to various internet lists where other people have complained about the same problems. I gave them detailed descriptions of how my digital darkroom is set up including distances from PC, speakers, other peripherals, etc.
I got no troubleshooting advice (none!). I got no replacement. I got no refund. What I did get was the same defective scanner sent to the wrong address! This is customer service?
One would think that with three weeks to work on a scanner, Canon's "Senior Technician" (as I was told) would be able to understand the problems and fix them. I wonder if they even took the scanner out of the box!
So, I'll make due and stop whining. I'll get a longer USB cable with better shielding and place my scanner farther away from other electromagnetic fields. I will also buy VueScan so I can do multiple passes and control the exposure better. If anyone has any other tips for reducing dark noise I would appreciate the help. Many thanks!