Lotem 800, exposing problems.

[Petkovski]

Hi. Im new to this forum, and searching i found a lot of questions and helpful answers, so i thought you guys might help.

Im working in a printhouse as a graphic designer, prepress and it geek. Recently they brought up the Lotem 800 with the Brisque workstation. I can't believe they brought that shit and sold the trendsetter 800 III quantum. I think the boss is having a hard time managing resources.

Anyways, I'm new to this lotem so i started configuring it and learning it. It's a model with 24 diodes, and on this machine only 17 are active, they need to be changed. After several tests, i noticed that on screen sets below 175 lpi, we're talking about 150, 133 and below, some strange lines are appearing all over the exposable area on the plates. I want to notice that these very thin and fine lines can also be found in very fine halftones or transparent colors, (20%K, 50%M etc etc.). On print, they look terrible.



Is this an issue with the non-working diodes? Also, i had to slow down the drum speed to around 600 - 800 rpms, since on higher drum speeds the lines were more intense. (How much is the maximum drum speed anyway?)

So... does anyone had this problem with the lines? I can't connect the dots through my head how is this related to the non - working diodes, or to the wokrking ones either? Maybe it's an issue with something else?

Also, how much do this diodes cost, and is there anywhere in Europe available to buy? Do they need to change one by one, or a whole array of 12 + 12 needs to be changed.

Please give me some advice.
Thanks.

[ansoft]

These line may be caused because of the white oil felts supporting the head. They need to be silicone oiled and replaced every year. From your message I understand that you don't have problem on 175lpi, but you experience problems on 150 and 133lpi. It is very very strange. Do you use these lpi on different resolution from 2540dpi? Please verify the screen set!
Luck!

Ansoft

[ansoft]

Laser diodes of Lotem 800V are very very robust.

[PACH]

Hi. Im new to this forum, and searching i found a lot of questions and helpful answers, so i thought you guys might help.

Im working in a printhouse as a graphic designer, prepress and it geek. Recently they brought up the Lotem 800 with the Brisque workstation. I can't believe they brought that shit and sold the trendsetter 800 III quantum. I think the boss is having a hard time managing resources.

Anyways, I'm new to this lotem so i started configuring it and learning it. It's a model with 24 diodes, and on this machine only 17 are active, they need to be changed. After several tests, i noticed that on screen sets below 175 lpi, we're talking about 150, 133 and below, some strange lines are appearing all over the exposable area on the plates. I want to notice that these very thin and fine lines can also be found in very fine halftones or transparent colors, (20%K, 50%M etc etc.). On print, they look terrible.




Is this an issue with the non-working diodes? Also, i had to slow down the drum speed to around 600 - 800 rpms, since on higher drum speeds the lines were more intense. (How much is the maximum drum speed anyway?)

So... does anyone had this problem with the lines? I can't connect the dots through my head how is this related to the non - working diodes, or to the wokrking ones either? Maybe it's an issue with something else?

Also, how much do this diodes cost, and is there anywhere in Europe available to buy? Do they need to change one by one, or a whole array of 12 + 12 needs to be changed.

Please give me some advice.
Thanks.

The maximum drum speed is 900rpm.
Laser diodes are expensive . You need a technician with a Spicer to relace the diodes.
Which diodes are faulty?
The faulty diodes do not work so have no effect on the output.
are the lines arround the Drum? Top to bottom of the plate?
Shame about the Trensetter as a 24 beam Lotem800 is slow compared to a Quantum.

[Petkovski]

Here are the specifications on the screen set
175 is at 100 resolution and frequency of 5.something
150, 133 and below are on 80 dpm (i think it's dpm) resolution

i think that diodes from 2 to 17 are active, don't know i have to check tommorow at work.

about the lines, there are everywhere from top to bottom on the exposable area. and there are striclty uniformed and parallel.
the lines are vertical H... first we thought it was the plate developer, but we tried developing plates in several partner companies. no luck. we tried different plates too.

so basically, what happens if i some of the diodes are dead? is it ok to put the machine at the optimal speed, let's say 850? even 900? because i think that higher speeds produce more lines.

also, i really need some info from where i can buy diodes and how much they cost? we plan to update the whole set with brand news.

thanks for your help! really apreciate it!

[PACH]

Here are the specifications on the screen set
175 is at 100 resolution and frequency of 5.something
150, 133 and below are on 80 dpm (i think it's dpm) resolution

i think that diodes from 2 to 17 are active, don't know i have to check tommorow at work.

about the lines, there are everywhere from top to bottom on the exposable area. and there are striclty uniformed and parallel.
the lines are vertical H... first we thought it was the plate developer, but we tried developing plates in several partner companies. no luck. we tried different plates too.

so basically, what happens if i some of the diodes are dead? is it ok to put the machine at the optimal speed, let's say 850? even 900? because i think that higher speeds produce more lines.

also, i really need some info from where i can buy diodes and how much they cost? we plan to update the whole set with brand news.

thanks for your help! really apreciate it!

Many things can cause lines on plate:
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
Problem could come from the Brisque: TSP board; fragmented files ( do an FSCK on the Brisque)
In the Lotem you could have a faulty LDD board ( this is the Laser driver board)
Faulty DDB board ( big board in the L BOx where the diodes are)
Could be a Lead screw problem/ Stepper motor/ coupling to the Lead screw.
As I said that the diodes are expensive and the technician needs a splicer as the fibre cable needs to be fused. Where are you? Maybe you can find help in your country.

[Petkovski]

Many things can cause lines on plate:
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
Problem could come from the Brisque: TSP board; fragmented files ( do an FSCK on the Brisque)
In the Lotem you could have a faulty LDD board ( this is the Laser driver board)
Faulty DDB board ( big board in the L BOx where the diodes are)
Could be a Lead screw problem/ Stepper motor/ coupling to the Lead screw.
As I said that the diodes are expensive and the technician needs a splicer as the fibre cable needs to be fused. Where are you? Maybe you can find help in your country.

im in macedonia. several experts came from bulgaria and serbia, and none of them had any clue.

[Petkovski]

huh.... i've read your post again and again... the problem could be practically everywhere, its a complex system. but anyways really thanks for the advice.
p.s. does no one knows how much these diodes cost??

[ansoft]

Dear Petkovski,
I dare to give you several advice:
1. Work on 2540dpi=100dpmm on this Lotem 800V. The lpi is whatever you want-175lpi, 150lpi, 133lpi.....etc.
2. Switch on all the diodes from the registry. If there is a problem with a diode the Lotem automatically will decrease the laser diodes numbers and will write you a message for working with reduced number of diodes.
3. If the problem is in laser diode driver-it needs replacement.
4. If the problem is in the DDB, which is not very common problem-it needs replacement.
5. It could be problem in the Brisque's disk drives. Please check the disks.
6. Laser diodes in Lotem 400 and 800V and 800V2 are very robust. For these years I am a service engineer, I have never changed a laser diode on such a machine. I have changed a laser driver, but a laser diode-never!
7. As PACH told you, clean the V groove and check the white pads. Oil them with silicone oil. It seems to be this problem.

It is a complex system, but you can manage.

Good luck!

[Petkovski]

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