Ink jet colour imbalance problem

At a guess, there's some crud on top of a colour-calibration photodiode somewhere inside.

Cheers

Phil Hobbs

poster

less

postal

The

is

Is that part of the printer hardware? like the auto-exposure photodiode inside a photocopier? ie not in the ink-jet carts. Time to explore the innards of one of those junkers in the mule-park, I think, to get the hang of ink-jet general operation.

I'm not sure if the printer does self-calibration, but if it does, the cal PDs will be part of the hardware. It doesn't sound like a nozzle problem, since it doesn't get worse, and the self-clean feature doesn't change it. It doesn't sound like a contact problem, because changing the cartridges doesn't change it. So I'm just guessing that there is some internal calibration being done, and that one of the PDs is dirty, which would move the calibration point in a nice repeatable way as you're seeing.

Cheers

Phil Hobbs

That would perhaps be an Epson Stylus Color 915 or an Epson Photo Stylus 915? They're quite different printers.

That's not quite what happens when there's crud blocking the photo diode. When some of the light is blocked to the photo diode, the mechanism thinks that the printer is printing too lightly, and compensates by applying more ink to the paper (making a drippy mess). If the paper looks like there's far too much ink being applied, it's probably a clogged photo diode.

The only the time there's a change in color balance is when the print calibration routine is run. It first prints a test page with psychedelic patterns, colorful stripes, and bizarre blotches. It then scans the printing with the photo diode and eventually compensates for any color alignment (convergence) and balance errors. Between calibration runs and print cartridge changes, it stores the settings in NVRAM.

However, a 30% difference in color balance is more than what I believe the printer can normally compensate. Something else is wrong. I'll wait until the correct model number is disclosed so I don't waste time on the wrong printer.

poster

says Epson Stylus Photo 915 on the front

I can't find any specific documentation on sensor cleaning online. I'll be visiting the local authorized Espson repair station next week and will try to extract some info from them.

Meanwhile, I've seen color balance problems change when printing on different computers. One computer prints fine, while the others print strange colors. I eventually traced it back a trashed color profile file (*.ICC). Try downloading a new file and try again.

You can also get some weird colors if you select the wrong type of paper, but not 30% error. Check the paper type anyway.

Check the waste ink pad. If it's saturated with ink (or dripping ink out the bottom of the printer), it should be replaced. When saturated, it tends to slop ink all over the print heads, resulting in a "dirty" looking color print. If all your colors look like a little black is mixed in, that's your problem.

If you don't think it's the computah, you can run a test pattern from the front panel and remove the computah from the equation:

Do the colors look normal without a computah involved?

Also, check the head alignment utility again:

If you're really desperate, there's the Epson service utility:

which can be used to tweak the carts. However the Stylus Photo 915 is not listed as a supported printer, so you may have problems using it.

poster

less

postal

The

is

I worked out how to get to the active jet face. remove both carts and unclip their top clamps Remove the ribbon shield, hidden plastic tang and nib at the rear Undo the 2 obvious screws lift the subassembly away from the carrier, slight joggling required no obvious opto device underneath

Cleaned the active face with alcohol and replaced , but no change in colour balance At least I've not made it worse (if it ain't broke, don't poke)

Perhaps its an unintended consequence of doing resets, something stored erroneously somewhere