HP CLJ 2840 prints 2" from top & runs off bottom of page

[sbtiti]

I'm working on a color Laserjet 2840 that, even with an internal test page print, prints to low on the page. There is no bottom margin, the start of the test page print is 2" down from top of letter paper. I have checked the registration rollers and they are good and clean. I have replaced the DC controller board and cleared the nvram all to no avail. The quality of print is fine and colors are aligned. Sometimes, especially on multiple page prints, it gets a paper jam & gives a message about wrong paper size. Each time I print the Supplies Status Page they look the same as the last one I printed: big top white space and print runs off the bottom of page. I have a service manual, but not sure where to start the troubleshooting at this point. Any help would be greatly appreciated. Thanks.

[sbtiti]

Sorry, I forgot to mention that the engine test also has the same problem. It starts about 3 cm down and runs off the bottom of the letter paper. Also it doesn't matter if the paper comes from tray 1 (mp tray) or tray 2.

[Lance15]

My guess would be maybe the rotary drive assembly. Has a solenoid in it that needs to be re-padded. Have done a bunch on the 2500/2550 printers.