Howtek D4000 vertical streaking

[georgl]

I recently bought a Howtek D4000 drum scanner, the first scans were fine. I cleaned the drum and lens and then noticed vertical streaking. I noticed that pads on the right side of the drum were missing and I switched to the other, nearly new drum - now it runs much smoother even at higher speeds. Pads, calibration strip, belt - everything looks fine, but I still get streaks?

What could this be? How can I solve it? Could there be dirt on the encoder? It doesn't seem to be a serious hardware issue - works 18 years and fails the second day I own it...

[Chris_Brown]

This doesn't look like an electronics/optics issue.

Are the streaks in the direction of the drum rotation or in the direction of main rail movement? (They are perpendicular to each other)

If the streaks are in the direction of drum rotation, then it could be that the drum sled is not moving along the main rail smoothly. There is a specific lubricant for that main rail. And the side guide rails need to be perfectly clean, without any pitting or corrosion. The guides resting on the guide rails should be free of debris.

If the streaks are in the direction of sled movement, then the drum is not rotating smoothly. Check the belt for cracks or sagging. Check the pads (like you did). Check the attachment pins and make sure the butt end is securely attached (no slop).

Also, what scanning software are you using?

Check with this group for specifics on everything related to drum scanners.

[georgl]

Thanks, I already contacted Aztek, I guess it's the old belt...

[deanwork]

It is hard for me to tell from this jpeg but I have this scanner and have used and even worked on it for about 8 years.

First absolutely replace the belt. Usually the belt causes a fringing only on the edges of shapes, making lines look frayed and fuzzy. I can't tell from your pic if that is what is going on and it isn't streaking.

The situation that I ran into with this exact Howtek was the LEAD SCREW ENCODER DISC.  I ordered it after Aztec told me this sounded like the problem. I can't remember but it seems like it was about $100.00.  This is a thin aluminum disc with codes stamped on it telling the scanner how to scan the drum along the lead screw (the thick silver rod that the drum moves along). I took the back off the scanner and got in there and replaced it and that fixed my Howtek and it has gone for many years after that and I've never seen this situation since. It isn't difficult to replace really if you take your time. There is a manual around to do this. You don't want to go through all this until you've eliminated all the other options Aztek gives you.

My streaking was color bands filled with noise and I couldn't solve that any other way.

Absolutely do join the yahoo scan-high end list to post this kind of question. http://tech.groups.yahoo.com/group/ScanHi-End/

John

[georgl]

Thanks a lot!

I got my hands on some replacement belts (the old one was really lengthened) but the problem is still there... Here is another 200% crop. Is this how it looked?

I've send a mail to Aztek, got an holiday notification and send another mail after holidays - still no answer...

[deanwork]

Yes that was what I was experiencing with the damaged lead screw encoder disc. This does not look like the belt problem fringing the outline of objects.

The guy at Aztek who helped me trouble shoot this was Evan. He was by far the most helpful soul over there that I have spoken to.

Send Evan that jpeg and get his advice. He may suggest something else to try first before trying to replace that part.

I was having this exact same pattern. However it extended the entire length of the scan and often displayed odd coloration as well. But that is the thing I was experiencing.

Also someone told you to lubricate the lead screw. Do NOT do that with the D4000 unit. Aztek told me absolutely not to lubricate it as with some of the other Howtek models. If you did lubricate it clean it off with a soft cloth. I would go in there and do that anyway. If some gunk got onto that lead screw calibration disc that could possibly cause this artifact.  Unfortunately you can't get to that part without taking the back off of the scanner and tearing it apart. But you might be able to spray come compressed air back in there so see if that helps.

John

[Chris_Brown]

The guy at Aztek who helped me trouble shoot this was Evan. He was by far the most helpful soul over there that I have spoken to.

He's the man.