Samsung ML 2850D

[Kavics]

I have a very stupid problem with this machine!
I wonder if you have any idea or experience with it.

It prints perfectly the single sided documents, and the even pages during duplex printing.
But the uneven pages are foulty.
It compresses the first two lines of the text into a horizontal black line.
But the line isn't as wide as the text, it's as wide as the page is.
All even pages are good, and all uneven pages are wrong.

When I cleaned most of the grease from the clutch witch drives the toner cartridge, the problem disappeared immediately for a time, but a few days later it returned.

There is no visible wear on the surfaces of the clutch, the whole machine is in good condition.
The problem isn't toner related.

As the paper sensor for the paper coming from the duplex is closer to the drum than the sensor for the paper coming from the paper cassette, a clutch problem could explain the compression of the lines.
But what is the black line over the margin?
Motor problem, whitch causes some electric "noise"? But than why is reacting immediately to a clutch cleaning?

Any idea?

[blackcat4866]

I've seen something similar on a ML-2851. I don't remember what the meter count was, but it was low, when the fuser gears started to grind themselves to dust.

Replace fuser coupler gear 37 (JC66-01637A) and heat roller ring gear 45 (JC96-01254A). Lubricate heat roller bushings sparingly with HP500 high temp grease. The part numbers may be different for the ML-2850.

Also try swapping in an OEM toner cartridge. Certain brands of refilled cartridges can be too hard to turn, and can briefly stall the main motor. I'm sure a person could calculate the proper amount of torque it takes to drive the cartridge, but the "OEM" method works well enough for demonstration purposes. =^..^=

[Kavics]

I didn't check the fuser itself, only the main driving assy. The gear which connects to the fuser seemed surprisingly worn inspite of the good general condition of the printer.
But I wouldn't think the fuser could cause this problem.

It seems first I've used wrong word: Uneven instead of odd.
When I print in single sided mode it never makes any mistake.
When I print in duplex mode 2nd,4th,6th,8th,10th,12th...... pages are always good.
But in duplex mode 1st,3rd,5th,7th,9th,11th... are always foulty.

Sometimes under the thin black line can be seen the first visible line of the text (Which is really the 3rd) is slightly compressed. The whole text properly positioned on the sheet. All lines are clear.

Two original Samsung cartridges were used to test the machine. Both cartridges work properly in other similar printer.

First most of the grease was wiped out from the spring type clutch. After it from the first try it worked well.
About a week later when the customer told it was wrong again, I hadn't with me the proper tool to dismantle the clutch, so I dropped some solvent on the spring, turned the gears forth and back, to wash out some grease.
After this, it worked again well. But I don't know how long.

But what can cause a thin sharp black line from edge to edge on the sheet?
And only on odd pages?

I wouldn't buy a main motor unnecessarily as it is'nt an expensive printer, the customer wouldn't be happy if I waste money on unnecessary parts.

[blackcat4866]

... It seems first I've used wrong word: Uneven instead of odd.
When I print in single sided mode it never makes any mistake.
When I print in duplex mode 2nd,4th,6th,8th,10th,12th...... pages are always good.
But in duplex mode 1st,3rd,5th,7th,9th,11th... are always faulty....

It's all the same to me.

... Sometimes under the thin black line can be seen the first visible line of the text (Which is really the 3rd) is slightly compressed. The whole text properly positioned on the sheet. All lines are clear.

Two original Samsung cartridges were used to test the machine. Both cartridges work properly in other similar printer.

First most of the grease was wiped out from the spring type clutch. After it from the first try it worked well.
About a week later when the customer told it was wrong again, I hadn't with me the proper tool to dismantle the clutch, so I dropped some solvent on the spring, turned the gears forth and back, to wash out some grease.
After this, it worked again well. But I don't know how long.

But what can cause a thin sharp black line from edge to edge on the sheet?
And only on odd pages?

The cartridge clutch is probably slipping periodically. The thin line is probably a compressed line of text or just toner shaken loose from the cartridge by the concussion of the clutch grabbing again. Your method of "washing out some of the grease" is a little too unscientific for me. If you cannot disassemble, clean and re-grease the clutch, then replace it. Use either Canon silicon clutch grease or IBM23 Clutch Grease. You cannot substitute just any grease or oil in a greaseable clutch. You'll get unpredictable results. Regardless, Clearly you have identified the clutch as the culprit.

Here's my guess why it would affect odd printed pages only: The additional drag of the duplex rollers/clutches is enough to make that clutch slip. Or maybe the paper is curled from the first pass through the fuser and the curled paper is experiencing "flip". Flip is when curled paper cannot be adequately attracted to the drum because of the direction of the curl. As the trail edge of the paper approaches the drum the trail edge "flips" pulling away from the drum and compressing the image. Try some fresh paper. I think you'll be pleasantly surprised.

...I wouldn't buy a main motor unnecessarily as it isn't an expensive printer, the customer wouldn't be happy if I waste money on unnecessary parts.

Don't order the main motor. It won't fix your problem. =^..^=