HP3520 - heads are clean test pages excellent, yet documents printed are almost illegible

[Barnesws1]

I have a 3520 printer, can provide serial if needed.

I cannot print a legible document (if I scanned one I printed there'd be nothing to see!)

However, all prints tests (clean printer heads, print reports) come back excellent and they are printed off perfectly

Can anyone point me to a solution?

[Barnesws1]

Just bumping in hope someone knows what to do? 

Don't want to buy new if can fix easily enough

Thanks

[Barnesws1]

I uninstalled and then reinstalled the software but no luck