HP CLJ4550 loses a single color, intermittently

[blackcat4866]

Thats the extent of it. If I print 3 prints of my test pattern, magenta may be absent from the first page, yellow & cyan may be absent from the second page, black might be absent from the third.

I've ruled out any sort of cartridge problem, simply because it affects all the colors intermittently, randomly.

I suspect some problem with the cartridge drive in the carousel. I nearly got it out, too, but something was keeping it in there....

Question 1) Am I on the right track with the cartridge drive train?
Question 2) How does the carousel come out? Do I really have to remove everything off the right side of the printer?
Question 3) What else could cause this?

Print quality looks great on the colors that I get. And I never lose the same color on two consecutive prints. Very strange. . . . . .

[prntrfxr]

Had this problem before. Try:

1.) clean/replace carousel positioning sensor
2.) toner carousel drive asm RG5-5502

Hope this helps.

[blackcat4866]

Thanks, I'll give it a try. More later.

=^..^=

[Copier_Guy]

I've ruled out any sort of cartridge problem, simply because it affects all the colors intermittently, randomly.

I also wouldn't be too quick to rule out cartridges. I had a problem once that was similar to yours with a 4600.

All the colors would randomly not print or wash out intermittently. I figured it couldn't be the cartridges because I found it hard to believe all of them would fail the same way at the same time.

I looked at the drives and ordered a new transfer kit to no avail. I was going to start ordering electronics but wanted to try a cheaper fix I hadn't explored yet.

Finally, I got the guy who sold the client the cartridges to send a new set and, GO FIGURE!!!

All the cartridges were failing the same way and in a strange fashion I've yet to see again.

If they're compatibles, definitely check. If they're OEM, check anyway. You never know.

Good Luck!

[blackcat4866]

They're Elite cartidges. Ironic, isn't it.

If it was fading I might think the same thing. I also changed Magenta and Yellow, to no effect.

Here have a look at the prints (they're supposed to be equal sized blocks of CMYK): (OK, so I won't. My pdf won't upload after 4 tries)

[Copier_Guy]

It's OK about the PDF,

I guess if you swapped out yellow and magenta and the problem still exists with those colors, you've pretty much ruled out the cartridges in my mind.

Wish I could help further. I never had to take out one of those Carousels on that box and I don't have the manual for it.

Please let us know how it works out and good luck.

[fixthecopier]

I think you are on the right track with the carousel. It has to push each cartridge out to make contact as it gets into position. It is a bitch to remove. Yes you pretty much have to gut the printer to get it out. It will be eaiser the second time when you have to go back in cause you forgot to put a screw in. Good Luck.

[blackcat4866]

Well, so far I've cleaned P10 carousel position sensor. It was buried in purple toner, but cleaning it made no difference. I removed the sensor to see if it was working. The carousel errors out after about 10 degrees of rotation without the sensor, so clearly it's functioning at least partially. The carousel makes crisp, accurate 90 degree rotations when developing. (I marked the top position on the left end of the carousel frame, and a registration mark on the outer frame, to see if the position was varying. It was dead-on every time.)

I did notice that occasionally the carousel would visibly wobble at one of the positions, randomly. There was gear noise to accompany it. I suspect I'll find a stripped section of gear, or maybe another pile of purple toner packed into the gear teeth.

I'll dig into the carousel drive Monday. Thanks all.

=^..^=

[blackcat4866]

Found two things:

1) A couple of the delrin bushings in the carousel drive pack were ovalled out significantly. The affected shaft drives the individual cartridge agitation.

2) On the cyan cartridge one of the alignment features on the cartridge is busted off (re-filled cartridge: probably gone before the last re-fill).

The carousel drive was not so hard to get out once I got the machine back to the office, and could spread out a little bit.

More later.

[blackcat4866]

Well, I'm sure the bushings helped, but did not fix the problem.

There are two one-way gears in the drive assembly. The first drives the cartridge agitation. The second (the one that was slipping, RS6-0182-000) cams out the cartidge, engages the agitation drive, and makes the bias contact.

Happily, its working after soaking in alcohol then lubricating with light oil.
It's much easier taking out the drive pack the third time.......

Thanks for the help/advice.

=^..^=