Problem with 1/4" vertical area in in Zone 6 not imaging on 4th unit of QM-DI

[djicewolf]

Yesterday we were imaging a plates when we noticed a unimaged vertical strip of about 1/4" on the 4th DI unit. After several attempts at restarting the press as well as sending other files it still remains. This am I tryed the band test plate and noticed it is in Zone 6 of the Diodes. Do you think this is a bad diode or some other issue with the controller. Any advice would be greatly appreciated.

 

[mrheidelberg]

you said the unimaged strip was a 1/4 inch in width ...... a normal diode is wider than this and because it is showing up on the 60% diode test it may not be the diode so it could be something on the glass strip on the laser carriage , make sure the glass is clean especially around the area of the issue.

 

[djicewolf]

Thanks for you reply,
We have carefully checked and cleaned the lens glass and I have just changed the diode then imaged a plate and the problem is still there. When I image the calibration plate on unit 4, occasionally the 1/4" missed area images approximately 2mm in the center, with missed strips on the edges. Then on the next attempt, misses the same 1/4" strip on Zone 6. I wonder if it is a problem with the control board?

 

[mrheidelberg]

What type of QMDI do you have ?

 

[djicewolf]

1997 Classic QM4-Di, I switched Diodes around from 5 to 6 and tryed replaced the diode with a spare and to no avail the problem is still there.
I also pulled and replaced all the connecting terminals. The only other thing I never tried was zero off all the diode setting in Unit #4, check the 60% Calibration screen in the event there is one diode maxed out and the imbalance may be causing the issue. What do you think.
Again thanks for the reply.

 

[mightyandy]

I had a similar issue on our PU4, it turned out to be dried magenta ink on the lens which dripped down from PU3 after applying to much roller wash.

We had already cleaned the lens several times without resolving the probem. It wasn't until I followed the advice from Paul on this thread I resolved my issue.

http://www.colorprintingforum.com/direct-imaging-offset-press/lens-cleaning-3741.html

 

[qmdipress1]

If it turns out to a Laser driver module send me an email.....

 

[Paul Cavanaugh]

If the problem is moving it is more than likely a laser drive module getting ready to go bad. It can also be from being low on water in your cooling unit causing the LDM's to over heat while imaging. Another issue that can cause it is have your cooling unit turned down below 23 Celsius. When it is turned down too low it causes condensation to build up on the electronics. Water and electricity typically are not good partners.

 

[qmdipress1]

Paul
I see the condensation electrial,imaging problems all the time....

 

[djicewolf]

Great News! I took the N/O Side cover off and unpluged then repluged the connectors on the Laser Drive Modules for the PU4 and then followed Pauls advice with the lens cleaning proceedure and we now have all the diodes imaging correctly. The unfortunate part is I can not directly attribute what resolved the problem, I am inclined to believe it may have been a dried ink speck on the lens So many thanks to each of you replying to my problem. I must check the forum more often and hopefully I may contribute something back as I have had this DI now for over 5 years and have been fortunate enough to fix any issues we have ever had.