Howtek D4000 vertical streaks

[georgl]

I recently bought a used Howtek D4000 drum scanner. I scanned two slides which looked fine. On the following scans I started to notice "vertical streaks" over the whole image. They are aligned with the drum rotation, so they are not related to the lead screw!?

I added a sample with some sharpening to enhance the effect. These streaks are visible all over the image.

It took me one month to get my hands on the lubricant for the lead screw, the scanning material and fitting belts - Aztek send a holiday notification mail, I repeated my request after the holidays, but still no answer...

- I cleaned the scanner
- I used the clean and nearly-new drum
- put the slides on different positions of the drum
- replaced the belt (it was lengthened)
- lubricated the lead screw

But I still have these streaks! I'm going crazy! What else can I do?

I don't know what to do! Help! Thanks....

[georgl]

The forum reduced the image size... So just the crop @ 200%

[Edwin Beckenbach]

Did you replace the drum pads?

Does the bearing sound smooth as it spins?

[uniB]

My D4000 has developed exactly the same problem, I've been meaning to get in touch with PS Electronics who I bought mine from to find out what's going on - just been waiting to get some money together to get it fixed. I'm pretty sure these guys will know what the problem is http://www.pselectronics.co.uk/

[georgl]

@uniB
Thanks! Could you keep me updated?

The pads are fine. It's even stranger: the very first scans without streaking were made with the worse drum already missing two pads - so this effect doesn't seem to be very sensitive about drum alignment! Some scans further I noticed the streaks and switched to the better drum.
The bearings sound fine, but I have no idea how it should sound!?

[IanMazursky]

There are a few things to look at.
1. Lead Screw lubrication. Since you just received it, i would clean and re lubricate it a few more times.
You would be surprise what they pickup over the years. Check the bearing all the way at the end of the right side, most of the excess lube ends up there.
Tons of stuff ie. dust and pieces of tape end up there. It may also be a greenish color which seems to be fine.
2. Room temperature. It should be between 65-75F. Colder then that, the scanner starts behaving weird!
My 7500 started acting up and producing line like that, the ambient temperature has dropped to 50F in my scanner room.
Both of my scanner (Howtek 7500 and Aztek Premier) don’t like it at all. I placed a heater at the air intake and after an hour she’s a happy girl again!
No more lines or errors.
3. Wear pads and location of film. Worn pads or the location of film can unbalance the drum.
This can cause areas of softness and a sound like the drum is trying to fly away. Try to place film in the middle of the drum and replace the pads when they don’t have a rounded top to them.
4. Drum belts. Those probably wont have much effect on the scan as they are connected to the rotation encoder and that compensates to some degree of wear.
But they should have very little slop and should not be marred, cracked or chipped in any way. If they are then they can start to disintegrate and its no fun to clean up.
5. Linear Encoder. This is something that is very dangerous to check (not to you but the scanner). This is the encoder that senses the position of the carriage on the lead screw.
Dust can clog the aluminum encoder disk and mess with the positioning of carriage. This can cause any number of issues.
You will have to disassemble the scanner case to get to it and its probably all the way on the left side of the lead screw.
A very light blast of air should dislodge the dust but be very careful, if you bend or damage the disk at all it will be ruined and its expensive to replace.
This is a last resort of things to check.
6. Scsi cables. They probably have nothing to do with the problem but make sure they are good cables and a good active terminator.
Bad cable can cause a whole host of issues, even the scsi card can contribute to problems.

Hope this helps and good luck!

[IanMazursky]

Forgot to add, try scanning the same image at different resolutions and apertures.
See if the lines show up at 4000spi and at lower resolutions.

[onnect17]

George,
I have a D4000 and I had the same problem at 4000 dpi. The only way I can get clean images is with a very soft rubber belt. Try the old belt.
Armando

[georgl]

First thanks for the suggestions, but so far nothing worked.

I compared the old (lengthened by >1cm) belt and compared it to the new [belt.jpg] looks identical to me.

I did a test with various resolutions (3000/4000/8000ppi) - while 3000ppi hardly shows any streaks, it gets worse at 4000ppi and horrible at 8000ppi - which is strange, because 8000ppi is just interpolated (same scan time) but sharper ? [streak2.jpg]

- streaks are always vertical -> it has something to do with the drum rotation, not with the lead screw ?

- it doesn't change with the belt

- it doesn't relate to the drum (pads, calibration strip)

- I warmed it up over several hours, turned up the room temperature (>20°C) - no change whatsoever

- it isn't affected by the film location on the drum - as far as I can tell

Can I somehow clean the encoder?

[uniB]

I'm waiting on PS Electronics to phone me back as Pete wasn't around today - should get back to me in the morning so hopefully I'll be able to shed some light on the problem tomorrow. I suspect it's got something to do with the Linear Encoder (I'm afraid!).