Laser Printer Repair Experts

Sure they do.
Something got stuck in the printer and dragged diagonally across the cyan and yellow drums, damaging them both in slightly offset positions. Now that they are damaged, the defect repeats down the length of the page in the same position for each color.

beowulff is correct. Image defects that repeat on the y axis are always caused by the drum, regardless of x pattern. Specifically, there is an abraded portion of the drum that is retaining toner. There is no other place that could cause this type of defect.

When you say “drum”, you mean this part, right?

beowulff’s explanation is how the same defect shows up on three drums (images post #15), correct?

Yes, those are the imaging drums. It looks like a foreign object passed through the printer and scratched the drums.

Okay, I’ve order the imaging drum assembly. They only cost just over $100 and that’s as much as I’ll spend on this.

I’ll probably report back after I install the new part.

Thanks to everyone for your input!

I see what you mean, and the repetition in both axes is curious, but what does do that?

Was the printer actually brand new and sealed up? Or had it been used?

Does anyone know how the LEDs are assembled in a printer like this? The pattern of the defect makes me think of how a LED bar might be made up of interlocking small blocks of LEDs. When the printer lights up a dot, maybe it says “Light up LED 10 in block 7”. The uniform trapezoidal pattern looks like it could be from individual LED blocks. It also looks like the LED block that is above and below would likely be curved along the horizontal part to match the concave/convex.

It is a laser printer. There is a laser that shines on a rotating polygonal mirror. The mirror scans the beam across the imaging drum to make each line of the image.

Actually, this printer might have LED print heads.
If so, it has four separate print heads, each positioned below their respective imaging receptors (the drums). I can’t think of a software or hardware problem that would cause a pattern to appear on each of the print heads. Since the image is assembled in one pass, each head needs it’s own bank of memory, so it can’t be a memory issue.

If I was the OP, I would remove the drum assembly and look at it closely, and see if I could find the damage on it. DO NOT TOUCH the drums with your bare fingers! Also, try to avoid exposure to bright light.

I did check beforehand and couldn’t find anything that indicated it has an LED array, as opposed to newer (but discontinued) Dell printers with “Clear View LED”. In any case, this PDF Dell printer marketing lineup doesn’t put the 2150 in the LED category.

Yup. Never been opened after 7 years.

I don’t think this is an LED printer. Did they have those in 2011?

I tried that, but I can’t get the drums to rotate at all. I assume that there is some sort of lock, but I can’t find it.

it repeats in both / each colors.

You can’t do that by smply draging diagnly (keybord fault)

Could a staple in a piece of paper cause that damage?

Maybe you could sell it as a printer with built-in document watermarking.

I think you can.

But, regardless of how the damage got there, it’s pretty clearly a drum issue. What else could it be?

Scanning mirror?

No way.
The laser scans one line a time. A line being equal to 1 pixel in height. Defects in the scanning mirror end up as lines down the length of the page.

The dual-axis periodicity of the thing is really, really odd, however, I’m still inclined toward damage in a drum or roller - if there’s a drum that is physically swept clean by something that itself has a rotary motion, then that could be the cause - a bit of debris caught on the rotating sweeping component is drawn across the drum, resulting in a dotted line of damage (a one-off occurrence) - then this dotted line repeats down the page forever.

I guess it could be a fault in the bearing or drive assembly of a scanning mirror that is causing harmonics that devolve to the two frequencies - across the page and down it, but I think that’s most unlikely to have manifest in such neat repetition as this.

It not at all possible it could be some sort of firmware glitch?

It looks like a physical, not electronic phenomenon.

Multiple repetitions of the same shape, degraded as if they are transfers one of another. Casting my mind back, I think I have seen something like this before when an already-printed letterhead page was passed through to have content printed on it - something went wrong and parts of the letterhead section melted off the page and gummed up imaging and transfer components inside the printer - and from that point on, every page that anyone printed, carried a mangled trace of the original letterhead (presumably it had formed something like a permanent lithographic trace on an imaging drum, or some such)