Dolev800V problem with dot density variation

[wpsy]

Hi,
I have a Dolev800V with harlequin rip and recently just found out the there is a dot percentage variation along the circuference of the drum. Very visible when output a double up (same two image in a large layout). You can see some dot percentage of one image is higher than the other by about 5 to 10% along the circumference of the drum. Run diagnostic test but all passed. Check the online processor also ok. Anyone who have such experience or expert please help. Thanks in advance.

[maxon]

You may have problems with your developer, replenish pump or dev circulation pump. Best thing to do at this stage is a uniformity test. Prepare a job 50 percent tint full film size and expose. If your film processor is offline, eject the exposed film and in total darkness pull the film out then cut it square so it fits the processor rotated 90 degrees. If the processor is online you should devise a way to intercept the ejected film in-between the dolev and processor.

[wpsy]

Thanks Maxon. I do make a flat screen test but the result is same. The screen from one side and the other have a difference of 5 to 8%. This is along the drum circumference. Thehihgest reading is somewhere 1/4 from the feedroller. I mean from the feed roller the screen is already a little higher than you set then it goes higher then reduce to normal as what is set. By the way I had an online processor.

[NJservice]

It could be the optics are slightly misaligned. Any spin motor device with this kind of problem could be caused by the spinner not being perfectly centered, so the image is slightly out of focus on one end of the film. Dmax and dot% will change slightly. I would clean the optics first, just to see if you get lucky, because on the Dolev, there are many jigs for alignment!
Also, The film could be coming away from the drum on one side, ever so slightly, making the same effect. It's been ages, and I don't recall, but is there some vacuum system holding the film tight to the drum? I'd suspect this if the 'worse' side of the image were the side held up against gravity.

[PACH]

It could be the optics are slightly misaligned. Any spin motor device with this kind of problem could be caused by the spinner not being perfectly centered, so the image is slightly out of focus on one end of the film. Dmax and dot% will change slightly. I would clean the optics first, just to see if you get lucky, because on the Dolev, there are many jigs for alignment!
Also, The film could be coming away from the drum on one side, ever so slightly, making the same effect. It's been ages, and I don't recall, but is there some vacuum system holding the film tight to the drum? I'd suspect this if the 'worse' side of the image were the side held up against gravity.

Also try and clean the vacuum holes with a needle.Spinner alignment is very complex and you need a technician with the correct tools and knows what to do.

[wpsy]

Hi, thanks. I have cleaned the drum and the optics also but still same. Now, I will check the spinner centering.

[maxon]

You must rule out the film processor though. You said result is the same, does it mean the darker band is now vertical as you rotated the sheet of film 90 degrees into processor ?
NJservice is right regarding film position. Load film with side covers open /bypass interlocks and before exposure starts take a look inside using a flashlight; pass your hand onto the film also to feel if it conforms to the drum curvature correctly. If the film buckles after the load sequence the laser beam won't be in focus in that area obviously. It takes half a millimeter to ruin uniformity ...

[NJservice]

... while you're at it (doing what Maxon says) shine the light really well on the film with bright lights in the room. When you clear that well exposed sheet through the processor, is it of stable DMax, or still strong on the lead edge? This eliminates the optics and laser from the equation and points to a replenish/circulation problem in the processor. Can the film be dumped into the bucket and taken to another processor, even in another shop? Do a full sheet of tint and a full sheet of solid for that. It's just that there's 100 things more to go wrong in a processor than most imagers, it seems.
If it's optical alignment, you'd probably need to call Kodak, and hope they had someone who remembers this stuff and has the jigs. Back when I was trained, I remember thinking "someone must have had a brother-in-law in the jig machining business!".
Good luck.

[wpsy]

Thanks for all the reply. The problem is really on the optics. I was finally aligned and the dot percentage is now even.

[NJservice]

nice!
Feels good to nail it!