Noritsu 2901 - ONLY White Prints - MLVA Lamp new, powered on and seems fine. What could it be ?

[Big Dave]

Hi all,

@kodakman7 had something somewhat similar, not really, but he got nothing as a response.,    I was hoping his issues were resolved and worked out, so I could apply his solution to OUR new problem.

For us it seems, all prints, daily setup, digital images, negative prints, are all Completely White.  No blue lines at all.  But the backprint looks just fine.  Correct order #, print #, filename, CVP, etc.

MLVA lamp is new and working well, output check for all dichroic filter motors in the printer MLVA section works well  (C-motor, M-motor, Y-motor), color wheel spins up just fine, MLVA lamp & fan turns on/off....   The ONLY problem with the output check is the sensors for the C, M & Y-filters  did not change from LIGHT to DARK when toggling the filter motors.. 

When operating the M-motor, the M-sensor would change from Light to dark, but after removing the MLVA lamp assy. and re-installing it, the M-filter Sensor quit going to LIGHT to DARK, and is now stuck at LIGHT with the other 2 sensors.   The dichroic filter rails are now newly greased, so they slide very easy and smooth.

Hoping for some assistance, thanks gentlemen !

Dave.

 

Edited November 28, 2022 by Big Dave

[phandinhha]

Please try to replace J390591, normally this PCB has no 5VDC output will cause white prints.

[PHOTOLABPART.COM]

RESPECTED SIR 

 

ANY ERROR THERE ? 

IF YOU NEED ANY PCB PLEASE CONTACT US 

 

[Minilab service]

Prints also will be white if missing pulses from color wheel sensor. Check sensor outputs. There should be pulses, which can see only with oscilloscope.

Check J/P285 on PRINTER I/O PCB3 :
pin 1 +5V
pin2 pulses
pin3 pulses
pin4 ground ( 0V )

If color wheels rotates, wheel is not broken inside, have +5V power supply, but no pulses then not working sensor board ( at the top of color wheel ) .

If have pulses on J/P285 then check do you have pulses on J/P280 pin 15 and pin 16 . Here output to printer control pcb.

[PAULOLAS]

Did you replace color developper? It is a specificity of RA4 that its activity can suddenly drop to zero when replenishment has been defective for several days. result is that you get white prints from evening to morning. Check with fogged paper. 

[Big Dave]

Hello, thanks for the replies, but everything is "normal" now.  Changed nothing, other than shutdown machine very early on day 1 and grease the rails the dichroic filters ride on.

Maybe dichroic filters stuck ? and not letting any light into MLVA head ?, but after greasing them on day 1, that was enough to get everything going again ?

The color filter motor sensors for C/M/Y wasn't changing from LIGHT to DARK, but after removing the lamp assy. and re-installing it, the sensors work as expected when testing the filter motors.  

Yesterday, Day 2 - everything was "normal" no issues, no error messages, nothing.
Today is Day 3 - and daily setup looks : as good as normal - prints are coming out as before.  
This type of issue I hate the most.  

@phandinhhaI did not check voltage there -- did not want to possibly mess something up if my fat hands accidentally short circuit something.  Will test and report if this issue comes up again.

@Minilab service Thanks for the suggestion, but still do not own an o-scope.... if the other power supply replacement is not a solution, can I attach a speaker to those leads and get a tone ?  is it a repeating pulse (tone generator) or a random variable pulse ?

@PAULOLAS Have not changed chems in a long time.

[Minilab service]

There 5V pulses. Can't connect standard speaker ( because they have low resistance ) . If you use beepers ( only if they have higher resistance ) then not sure, what you hear there. It is repeating high frequency pulses, so might be you will not hear them. More easy to get somewhere oscilloscope, or ask someone who has it.
First check 5V power supply on J/P285 pin 1. If it is missing then you have not pulses.
Yes, chemicals can be bad and prints will be white. I saw it few times and minilabs where newer ( even QSS37 ) . Check with fogged paper.

[kodak_service]

On 11/30/2022 at 10:39 PM, Big Dave said:

Thanks for the suggestion, but still do not own an o-scope.... if the other power supply replacement is not a solution, can I attach a speaker to those leads and get a tone ?  is it a repeating pulse (tone generator) or a random variable pulse ?

You can connect a standard speaker through a capacitor.

Edited December 3, 2022 by kodak_service

[kodakman7]

Hi Big Dave- my problem persists. I checked for responses to my earlier post for a while then stopped checking due to no responses.

My problem is sporadic and only (touch wood) at start up if it is going to occur. It doesnt suddenly go white during the day. Usually a single restart (power off @ circuit breaker) resolves and all is fine for the day. Very occasionally it may require 2 restarts. But then other days it will start up fine - say 2 days a week. Our chems are fine, lamp etc all good. Intermittant points to an electronic component. we havent been logging it accurately to now, however commenced yesterday. And the head scratching goes on.......