HP Color Laserjet 3500 - unexpected image problem

[hometown]

Replaced Front Cover Asm. RM1-0463-020. Had some trouble resetting arms that set the toner/drum units. Seems they were put off track. Reset the arms to operate correctly...or so it appears. This printer was working properly before I took on this seamingly simple job. Getting Error 10.92..."Cartridges not Engaged". Will, maybe, reset after openning Front Cover Asm or turning
the printer on/off. If printing is possible then the image is light and uneven
margin to margin. Also, at the right margin, various width sizes of a black band is shown...top lead edge to bottom. We've been told that it "could" be the Scanner Asm. or the Transfer Roller. Nothing is said about the possibilty of me upsetting something upon the install of the Front Cover Asm? Can't help to think that I've created this problem. Can you help? What do you think?
Thanking al of You in Advance for Your Help! - Hometown Boy -

[cs_steve]

Some advice from the Service Manual:

I would try Step #2 first -- cleaning the contacts / could be a toner spill interfering with contacts.

10.92 error -- described as: "The cartridges are not engaged., poor
primary transfer bias contacts, defective high-voltage supply, or control signal errors."

1. Reseat the print cartridges.
2. Check the printer primary transfer bias
contacts to the transfer unit. Clean if dirty. If
the contracts cannot be cleaned or they are
damaged, replace the transfer unit.
3. Replace the high-voltage power supply
PCB. - expensive, doesn't seem likely
4. Replace the DC controller PCB. -- expensive, doesn't seem likely

[redcow]

Sounds like you (the printer) has a timing problem. Somethings out of alignment.

[hometown]

Thank You Ladies and Gentleman for your Replies!
Worked with this one for 2 days. Finally discovered that a 1 inch square button with a compression spring was missing from the New Front Cover Asm. It applies pressure to the Image Tranfer Belt Asm to the Drum/Toner Units. The result of it not being there is a light image on one side(this case the left): as there are two of these buttons on the Front Cover. How did this button get lost? Who Knows? Who cares! Been doing this sort of work for 30yrs. or so. Fact is, I or we, so-called experienced Techs could Over-think the problem and Over-look the obvious! Has this ever happened to you? Bet it has! Advice to New-be-Techs: Don't assume anything! Step away from your work and take a more Object look at the situation. Don't toss those old parts until the work is a success...even after the job is done. Success must 'stand the test of time'.
Thanks Again, Regards, Hometown Boy