Lotem 800, exposing problems.

[nemo]

This thread is a month old, but if you still have the problem, follow Pach's advice:
"Take the back cover off and clean the V groove ( this is where the head moves)
On the bottom Left and Right handside of the Dynamic Optics) you will see White pads that need oiling with Silicon oil"
The lines you see are caused by vibration due to friction between pads and V-groove surface causing gaps between two consecutive swaths - wipe the V-groove clean and use the a bit of the silicon oil which came with the machine to lubricate it.
Do not use generic silicon oil as it may damage the V-groove surface - extremely expensive to replace.

[Armya Inc]

Thanks... I will start this week to sort out this mess, and step by step i'll try anything and i keep you updated!

This is called banding Issue. The Banding issue or thin lines on the plates are because of gaps caused between Laser beams. Replace the diodes, the issue will be resolved.

[VladCanada]

... and no word has been said - are there Negative or Positive plates?
So that could be either "banding" or laser modulation (some laser is ON for a short period of time with no reason to be ON) issues.

[Armya Inc]

... and no word has been said - are there Negative or Positive plates?
So that could be either "banding" or laser modulation (some laser is ON for a short period of time with no reason to be ON) issues.

It is a positive Plate

[Fii]

The same problem here, on Lotem 400F,24 diodes in array, positive plates. We cleaned the V-groove, repleaced pads, oiled screw and groove - problem still here. Also there was a problem wit diode array, diode nr 13 was almost dead, reasonably it could be the cause, when it died, and also working with 12 diodes only stripes were there, especialy on yellow seperation.
We got new diode from Kodak, that arrived in its antistatic plastic casing, but not attached to metal bar in casing and, bended contacts - 400 euros(or even more) straight to trash can. Ok, no big deal, it was not hard to replace #24 to #13. Basicaly, that canging process isnt such complicated you just need optics fiber soldering station and some tools, basicaly long ph0 screwdriver.
But, those bloody stripes ar still there, and there is no change after all of those procedures.

[diggs30]

hi we had similar problem over here after we were blamed because or plates and processor , the problem ended up been something on laser head scraping the plate , or something touching the plate when it was all vacuum down as the lines were dead straight

cheers
dirk

[Quicko58]

We saw similar problems on a Lotem with fine lines at random in the direction of drum rotation. In our case our plate/processor was being blamed. After extensive investigation into the processor & finding nothing wrong there, I had to prove if the Lotem was the cause.

By turning the plate through 90 degrees before processing you can narrow the issue to either the setter or processor. In our case this proved the Lotem was the culprit. On investigation the Kodak engineers discovered an intermittent problem with the lead screw and once that was rectified, the problem went away.
john

[Kevin@Kodak]

By turning the plate through 90 degrees before processing you can narrow the issue to either the setter or processor. In

Just to add to this: depending on your plate size and processor size, often just turning the plate 10 degrees or so is an easier/better way to distinguish imaging-created banding from processing-created banding (or even scratching). 90 degrees is often fine, but may also be too wide for your processor or get confused with banding in the other direction.

[kala]

Faced same problem

Here the solution :

1. if lines appearing on all the rulings then its related to non-working laser problems.
2. if its ok with 133 & 150 then change the expose settings for 175 its ok
3. if 175 ruling is the problem try the plate with fresh chemical and see the result if the lines are not visible in naked eye and its visible in printing then its related to expose settings

regards
kala