Diagnosing cause of thin black line on riso print from RZ370ep

[ianmck]

Prints from the title machine have a single thin black line down them as seen in image. The line can also be seen on the master. The TPH has been cleaned and there's no visible damage or dirt. Is this a fault with the TPH or could there be another cause.
Thanks for any help.

Ian

IMG_20211021_212655419.jpg

[slimslob]

Re: Diagnosing cause of thin black line on riso print from RZ370ep

If the master was generated by scanning an original, I would say that you have a speck of dust of lint on a mirror.

[jermyth]

Re: Diagnosing cause of thin black line on riso print from RZ370ep

Slimslob is most likely correct, but to confirm before cracking open the optics go into test mode and print out a test pattern, mode 80 is a checker pattern.
Good luck.

[ianmck]

Re: Diagnosing cause of thin black line on riso print from RZ370ep

Slimslob is most likely correct, but to confirm before cracking open the optics go into test mode and print out a test pattern, mode 80 is a checker pattern.
Good luck.

Thanks. The checker printed without the line, so it looks like dust on a mirror.