unprinted thin horizontal lines with constant intervals in laser color printer (m251n)

[Mortezash]

hi guys

my laser color printer, m251n, prints with unprinted horizontal lines with consistent and periodic intervals of approximately 7.5 cm (between same colors) and 2cm (between different colors)

for instance, the first unprinted line is black, 2 cm below there is an unprinted thin cyan line, 4 cm below there is an unprinted magenta, 6 cm below unprinted yellow, and 8 (7.5 cm is more precise) below there is again an unprinted black and so on...

i attach an image to describe the unprinted lines (it's not the real print, just for better understanding)

 

 

what is the problem?

[Repairatrooper]

The repetitive defect ruler for this model will help narrow down possible components that are causing the issue:

[Mortezash]

thanks for your help.

however, in the list, the only item that has 7.5 cm interval introduces the opc drum mentioning it is on ONE plane color. but my problem is on all colors.

[Repairatrooper]

Do not discount the fact that you might have problems with all your cartridges. You may need to replace one to see if that solves the issue and work from there.

[Mortezash]

you are  right, the first practical solution is to try a new cartridge. however, theoretically speaking, I wanted to ask the community of printer experts as you, if there is a specific condition or problem causing this exactly placed thin unprinted lines. because I thought it is not so probable that all cartridges defects are the same and the position of the lines are equally distanced from each other. 

[Mortezash]

I just took a picture from a printed paper, as you can see the unprinted lines are uniformly happened with equal interval not only for one color, but between colors!

 (the distorted black line is due to perspective effect, all bars are straight with no curved shape)

[Mortezash]

after reading some materials about color printers, I think at a specific time with each rotation of drums, the optical laser is turned of for a moment and because of that all drums don't get electrically charged at this moment and make the uniform pattern of unprinted horizontal lines. Am I right? is this possible?

[Repairatrooper]

The laser could be an explanation. A bad high voltage board or one cartridge with a short in it might also cause a problem. We have seen a bad cartridge cause an issue with all colors due to a voltage drop. In the past, yellow was the most common cartridge we found. How is the power at the location? Have you tried a different outlet on another circuit?

[Mortezash]

thanks for your answer.

I'm not expert in printers, I'm a simple user. so if I understand well what you said, the power supply of our place is 220 vAC and is OK,

however if your text referred  to internal circuit of printer, I don't know about that.

[Mortezash]

I just thought little bit more about tge problem...

these are facts:

1. the interval of unprinted horizontal lines and one rotation of opc drum are exactly equal! this means that with each revolution of drum, the unprinted lines occurs (it triggers the event).

2. the inter-color interval is uniform and equal, it means that at the same moment, all printing actions stop and it makes unprinted lines, that because of constant distance between cartridges,  equally placed with respect to each other.

these facts lead me to think that your idea about existing a short circuit in one of the cartridges in a specific angle of drum position is right.

what do you think?