Epson ET-8550: horizontal banding mainly in neutral gray midtones despite clean nozzle check

[Cryptogene]

Hi everyone,

I’m troubleshooting a specific horizontal banding issue on an Epson EcoTank ET-8550 (Firmware: 05.51.OP28P8, Total pages: approx. 966) and would appreciate some technical opinions.

The issue is not general color banding. Pure or saturated colors are mostly clean, but neutral gray tones show very visible horizontal density bands. The problem is most obvious in light and mid gray values, especially around 10%, 25% and 50% neutral gray. Darker gray / black areas are less affected, and 100% black usually looks much cleaner.

What makes it interesting:
If I print color areas without any gray in the image, the colors look mostly fine. But when neutral gray areas or gray ramps are present on the same page, horizontal banding becomes visible, and some adjacent color areas show the same horizontal density pattern as well.

The printer currently uses compatible Epson 114/115 ink, not Epson OEM ink. Therefore I’m wondering whether this could be related to the Gray or Photo Black ink behavior, especially under midtone rastering load.

What I have tested so far:

• Multiple photo papers tested: no relevant difference
• Nozzle check looks complete for BK, PB, C, Y, M and GY
• Head alignment performed, both vertical and horizontal
• Paper path cleaning performed
• Translucent encoder film inspected and gently cleaned; it looked clean
• PB and GY channels/nozzles cleaned with Epson-compatible printhead cleaner
• Maintenance box C9345 replaced
• Power Cleaning performed
• Printer left powered off / unplugged for about 12 hours afterward
• Nozzle check still looks clean
• The gray banding remains

Print settings tested:

• Higher quality / slower printing improves the result, but only makes the bands finer
• Bidirectional/high-speed printing off improves it slightly, but does not remove it
• Disabling color correction does not solve it
• Different media settings change the appearance slightly, but the problem remains

Additional test results:

1. CMY test patches on glossy paper:
   • Cyan, Magenta and Yellow patches are much cleaner than neutral gray.
   • There may be very slight horizontal texture, but nothing as severe as in the gray patches.
2. Repeated gray bars:
   • The same horizontal banding appears consistently in light and mid grays.
   • 100% black is much cleaner.
3. Three identical gray bars printed at left / center / right positions:
   • The banding appears across all positions, not just one area of the page.
   • This seems to rule out a purely local platen or paper path issue.

My current thoughts:

• It does not look like a classic clogged nozzle, because the nozzle check is clean even after the issue appears.
• It does not seem to be paper-specific.
• It may be related to Gray / Photo Black ink behavior, neutral gray rastering, or midtone microbanding.
• A general paper feed / pass overlap issue might also be present, but CMY patches are much cleaner than neutral gray, so the gray rendering path seems especially suspicious.

Has anyone seen this kind of ET-8550 behavior before?

Could compatible GY/PB ink cause horizontal banding only in neutral gray midtones, even with a perfect nozzle check?
Or does this look more like a printhead firing / paper feed / micro-weave / internal calibration problem?


Clean-Test:



Stripes because of adding gray in the middle:


Gradient also affects colors massively:

 

[W. Fisher]

Since this happened with a non-OEM ink, maybe the ink has a different viscosity and maybe being thicker, might not clear some smaller nozzles as well as the OEM ink would?

I got issues with a non-OEM ink now too in the 3880 (below) that seems to have congealed and clogged up my printhead. First a few nozzles began showing some issues, and then maybe half. I noticed it when sucked out it seemed a lot thicker too for some reason. Bad batch maybe.

I'd try the OEM ink and see. But it takes a very long time and lots of prints before the new ink hits the head in my findings.

 

[Epatcola]

That is one bizarre problem.

I would try printing an obviously failing image from a USB stick or memory card to completely rule out computer/drivers/communications. I doubt it will make a difference, but, it is quick and easy to check.

To me it looks like any use of the photo grey channel is interfering with all or most of the other channels and interfering for a short time not just when used. That looks like an electronic/electric issue. Maybe something like the PG channel is overloading the power supply resulting is smaller drop size in all channels.

When did the problem start? If it was a 3rd party ink performance problem it would have started as soon as you filled it. Did you suddenly notice the problem and has it got worse?

The 3rd party ink has probably screwed your warranty. It is possible the 3rd party ink has damaged the printhead or maybe you just got unlucky. Is this 3rd party ink widely used?

Is there any possibility of spills or contamination of the printer driver PCBs?

 

[W. Fisher]

If you switched to a 3rd party ink, you likely will not see the damage - if that is the cause - immediately. It will slowly creep up on you, imhe.

For some bizarre reason, even though my repair or cleaning solution Vivid Magenta tank is filled with alcohol and WIndex, and it looks a faint blue in the cleaned and washed VM ink cart, when I print a magenta only letter-size page (RGB=255, 0, 255) it is still coming out magenta even after 15 full magenta color pages in PS, and after 3-4 power cleans and a maintenance tanks (And now another one!). The ink is creepy stuff that hangs around, forever it seems.

The only thing I can think of is if my ink lines and whatever is in the print head itself still has magenta ink "Clumps" or crud in them, maybe the cleaning solution is diluting that magenta ink crud in the lines and head and causing it to still print magenta pages, ad nauseam. Don't know, but I still see magenta pages even with a clear cart in its place, Wierd.

You might want to send your images to Epson Support and see what they say - but I'd stay mum on the 3rd party part. I don't think it should do that if new.