Cp1525n horizontal black stripes when start printing

1. Open the printer driver setup window
2. Click Custom Settings on the Maintenance tabThe Custom Settings dialog box opens.
3. Switch head alignment to manual
   Check the Align heads manually check box.
4. Apply the settings
   Click OK and when the confirmation message appears, click OK.
5. Click Print Head Alignment on the Maintenance tab
   The Start Print Head Alignment dialog box opens.
6. Load paper in the machine
   Load three sheets of A4 size or Letter size plain paper into the front tray.
7. Execute head alignment
   Make sure that the machine is on and click Align Print Head.
   Follow the instruction in the message.
8. Check the printed pattern
   Enter the numbers of the patterns with the least amount of streaks in the associated boxes.
   Even if the patterns with the least amount of streaks are clicked in the preview window, their numbers are automatically entered in the associated boxes.
   
   When you have entered all the necessary values, click OK.
   [img src="http://ugp01.c-ij.com/ij/webmanual/PrinterDriver/W/MX450%20series/1.0/EN/PPG/images/i_note.gif" alt="" >Note
   • If it is difficult to pick the best pattern, pick the setting that produces the least noticeable vertical streaks.
     (A) Least noticeable vertical streaks
     (B) Most noticeable vertical streaks
   • If it is difficult to pick the best pattern, pick the setting that produces the least noticeable horizontal streaks.
     
     (A) Least noticeable horizontal streaks
     (B) Most noticeable horizontal streaks
9. Confirm the displayed message and click OK
   The second pattern is printed.
10. Check the printed pattern
    Enter the numbers of the patterns with the least amount of streaks in the associated boxes.
    Even if the patterns with the least amount of streaks are clicked in the preview window, their numbers are automatically entered in the associated boxes.
    
    When you have entered all the necessary values, click OK.
    [img src="http://ugp01.c-ij.com/ij/webmanual/PrinterDriver/W/MX450%20series/1.0/EN/PPG/images/i_note.gif" alt="" >Note
    • If it is difficult to pick the best pattern, pick the setting that produces the least noticeable vertical streaks.
      (A) Least noticeable vertical streaks
      (B) Most noticeable vertical streaks
11. Confirm the displayed message and click OK
    The third pattern is printed.
12. Check the printed pattern
    Enter the numbers of the patterns with the least noticeable horizontal stripes in the associated boxes.
    Even if the patterns with the least noticeable horizontal stripes are clicked in the preview window, their numbers are automatically entered in the associated boxes.
    
    When you have entered all the necessary values, click OK.
    [img src="http://ugp01.c-ij.com/ij/webmanual/PrinterDriver/W/MX450%20series/1.0/EN/PPG/images/i_note.gif" alt="" >Note
    • If it is difficult to pick the best pattern, pick the setting that produces the least noticeable horizontal stripes.
      (A) Least noticeable horizontal stripes
      (B) Most noticeable horizontal stripes
      

check the printer head and roller inside the printer

also check the nozzle because it may be clogged due to some
dust

Black horizontal lines ( page is held Portrait ) ,
where print is affected the print image fails to show behind Line effect but shows in between-
the drum surface has been damaged ( likely wear and tear) and can no longer maintain an even layer of electrons due to leakage/short
solution:
replace the toner cartridge which houses the drum.

If this is a laser printer, it sounds like you have either a defective drum or transfer belt. Drum would be my first guess.

I received an answer elsewhere. Thank you.

Go to printer maintenance and perform deep cleaning, do this for 3 times. Then print nozzle check to see which color has a problem. If you still encounter your problem all you need to do is to replace your cartridge.

go through your printers software in your start menu and clean the heads.

go into the printer and do a test print. start>printer & faxes>right click on the printer in question>properties>printer preference button> test print ... try the printer's own test print. This is usually caused by a poor print head, low ink, poor cartridge or the need for calibration. Look in the maintenance tab in the printer properties for head cleaner, jet cleaner etc. This also happens with refill ink cartridges.

check your drum may the corona ware is broken . change the drum.

Sounds like a bad imaging drum to me...