Bad streaking on print xerox 8550 phaser

The best way to tell if your problem is clogged jets, or bad maintenance kit, or something blocking jets. Is to look at light stripes test, and see if missing jets are all in a straight row or all over the place. If the missing jets number less that 10 you can use jet substitution to avoid the streaks. If you are using Media Sciences or some other after market ink, check that most of your problems are not in the cyan area. Media Sciences produced a bad batch of cyan which clogged the jets pretty bad. The good news is that if their ink caused the problem they will pay for some one to come out and replace your printhead. If you LST (Light stripes test) has a smear the entire vertical lenght of the page. You have either a bad maintenance kit, or a piece of paper, lable etc..rubbing against the drum while printing

check your maintenance kit & you eliminate the probleme by enter to menu in the machine and look for a maintenance mode and activite the elimination This customer-initiated cleaning procedure is selected by choosing Remove
Print Smears on the Control Panel’s Print Quality Problems menu. This
procedure cleans ink out of the Preheater that may have been deposited
there. Heavier-weight, high-grade quality paper works best for this procedure.
Ink can also be deposited if a jammed print, with ink on it, was pulled
backwards through the Preheater.
In the Preheater cleaning cycle, these events take place:
1. The customer selects the Remove Print Smears menu item.
2. The printer overheats the Preheater to about 110o C, softening ink
trapped inside the Preheater. Ordinarily the Preheater runs at
temperatures of between 60o C and 70o C.
3. The printer picks and passes approximately 12-24 sheets of paper
through the print path. The first few sheets absorb and remove ink from
the Preheater. The printer continues to pass sheets of paper though to
cool the Preheater until normal operating temperature is reached. If
duplex capability is enabled, 5 sheets of paper go through the simplex
path and up to 20 sheets go through the duplex path.
4. The printer returns to the Print Quality Problems menu.
Because of the higher paper temperatures involved, this function can clean
the Drum of ink deposits caused by a contaminated blade on the Drum
Maintenance Ki

Have you nailed down jets that are plugged? If so, the advanced printhead cleaning process helps you to target specific jets. Also, if you manally printed duplex without telling the printer to go into 2nd side mode, you probably melted ink inside the preheater assembly. Run "Remove Print Smears" to clean this out.

You can try the "Eliminate Light Stripes" routine several times, but if that doesn't help, you may have a clogged print head. If you're reasonably handy, you may be able to replace it yourself. Contact DocJams.com for parts and directions; tell 'em MaverickSolutions.biz sent you - we get all of our Phaser parts from him. His prices are reasonable and his suupport is top-notch.

Have you tried Jet substitution? sounds like a bad cleaning blade or you need a new print head -Carl