Poor print quality

[Andrew8888]

I have black “GT stripes” down the page, whether printing in colour or black & white. I have tried all the troubleshooting suggestions in the relevant HP manual, including calibration, running a cleaning page and generating a print quality page. The manual suggests contacting HP where the lines run across all the colours on the print quality page. 
I am loathe to replace the toner cartridges at this point as the problem seems to be elsewhere. Please help if you know a fix. 

[Repairatrooper]

Please post a sample of what you are seeing. Are the stripes will bonded to the page or does the toner flake off?

[Andrew8888]

Image attached. 

Am able to scrape some of the black toner in the stripes off with fingernail. 

 

[Andrew8888]

Hi Repairatrooper

Thanks for your interest in my issue. 

An image of a print quality page is below. 

I am able to scrape some of the black toner off with my fingernail. 

 

[Repairatrooper · Accepted solution]

Either your black cartridge is bad or the transfer belt has failed. Remove the black cartridge and look at the blue/green drum to see if there are corresponding marks on the drum.

[Andrew8888]

Thank you. 
It’s the black cartridge (corresponding marks on drum).