asked May 23, 2014 at 12:09pm
Hp HP LaserJet 4

HP4 blotchy black streak down the center

My HP4 has a black streak about one inch wide and blotchy, all the way down the page, one inch to the left of the center. I took out the cartridge and there were toner blobs all around the long green cylinder, one inch wide, about one inch to the left of center. I cleaned the cylinder but when I put the cartridge back in I still had the same problem. I then changed to a new cartridge, but that didn't change anything.

I found an answer in this forum but it only applied to a streak down the left side of the page, so I don't know if the cause would be the same for a streak down the center.
If you see a streak on the drum, then it is due to a bad wiper blade in the cartridge. Cleaning the drum does no good because the blade that is supposed to keep it clean has deteriorated. Probably the other cartridge, even if it were brand new, expired years ago. The wiper blade in that would have deteriorated as well. If you turn the drum gear with your thumb it should clean the drum as it passes the wiper blade.
by moe on May 23, 2014 at 12:34pm Add comment
That worked, I think. I tried turning the original cartridge drum without cleaning it as I went along. The cartridge cleaned itself eventually. I put that original cartridge into the printer and printed some pages and they were streaked. But I noticed improvement. So I kept printing more pages. After 40 pages, the problem is gone. I wonder how the printer failed in this way and then cured itself.

The newer cartridge won't clean itself as I turn the drum, so I guess it's dead.

I hope the mysterious solution continues to work. I like this old workhorse HP4. I will be sorry to see it die.

Thanks for the help.
by McGyver_44 on May 24, 2014 at 9:55am Add comment
You can open them up and replace the wiper blade. Real easy. Just involves 6 screws, takes a few minutes.
by moe on May 24, 2014 at 2:48pm Add comment
Great. I can't find it in the website. What is the part number? Does it come with instructions? - McGyver_44
I think we're out of them. Here's the instructions if you can find one.
by moe on May 24, 2014 at 10:17pm Add comment
I have a cartridge that works. I have a spare that needs a wiper. So I’ll just wait until I run out or toner, then I’ll check back to see if you have a wiper. If so I’ll buy it and if not, I’ll just buy a new cartridge. I’m not going shopping around for a wiper at this point because I don’t want to buy from anybody else. Thanks for the instructions, and thanks again for the great forum support. - McGyver_44