Qmdi Problem with diodes 1 and 11

HELP!
I have a problem with diodes on unit 4
Diodes 1 and 11 will not burn
I have cleaned the glass and can't seem to find a break in it
I have changed the diodes still not working
No board error showing
Thanks
Bruce

 

It may be the control stage for the diode not working? your diodes you replaced may still be good.

 

Yes def not diodes may be a board or perhaps a loom?

 

an easy way to check the board is just to swap one from another unit and burn plate. if problem moves to other unit, it would be in the board.

 

We are having a little different laser issue. We had to replace our Black laser unit as our operator cracked the glass on the original one. (We have a "Plus"parts press that we steal from. We calibrated it with 60% screen but are constantly adjusting laser density on 3 to 4 lasers on this unit. It will not hold calibration from job to job. Before this happened, we did not have to adjust lasers hardly ever.

 

You have to replace the complete laserunit, the glass you broke is not from an individual laser.

 

We replaced the entire Laser Unit. We had a local x-heidelberg mechanic do it as he had the gauges. We then spent countless hours setting the zone offsets and densities as we did not have that information from the parts press. After setting densities using the 60% screen it will look good for a job or two then we are back to chasing diode densities on the next several jobs.

 

Ok, tought you only replaced 1 diode. Do you have air in the system. Deviation in temperature wil influence the power of the diode.

 

We will work on that. If there was air in the system would it only affect the black unit? Wouldn't we see fluctuations in the other 3-units as well

 

On the 'Classic' model the tubes were in serie and on a 'Plus' I tought the changed it to parralel. Do you change always the same diode's. Do you have to apply more power every time to them.

 

Ok,
My operator gave me his list of when he made recent diode adjustments here it is:
Cyan Unit:
01/05/14 #2 diode -2
01/06/14 #2 diode -2
01/08/14 #2 diode -5
01/08/14 #2 diode -5 (another)
01/08/14 #2 diode -3
01/24/14 #2 diode -2
01/24/14 #15 diode -2
01/24/14 #2 diode -2
01/24/14 #15 diode -4

Black Unit:
01/08/14 #7 diode +5
01/22/14 #7 diode -5
01/22/14 #9 diode -4
01/23/14 #8 diode -2
01/23/14 #9 diode +1
01/23/14 #12 diode +1

 

You sad trouble's on black after replacement but most correction are done on Cyan diode 2. On black diode 7 +5, -5 is a total correction of 0. Diode 9 corrected -4 andthe other day his neighbour is corrected -2. This doesn't look weird to me. Do you always use the 60 percent screen to adjust are do you look at the job you are running. What screenruling do you print (150 , 175 or 200 lpi)

 

marc,
I know cyan has been adjusted more recently but it's because of the nature of the forms we have been printing.
This morning we had a job with 20% black only tint across the sheet and had to make adjustments to 3-zones on the black.
We end up adjusting to the job most of the time because we can calibrate to the 60% but on a live job with lighter values the zones be obviously different and so goes the chasing zones.....We did add water this afternoon and bled the lines. 1-1/2 bars off and about 4-bars turned on. It did seen like we had some air in the system so we'll see how that helps tomorrow.

 

We are using 150-line