[Bastiaan]

All i can think of is to do several playbacks, and copy/paste the results back together in ptle. Also clean the dat's heads between each run. If you have access to a professional dat-machine...use it. They usually have better quality heads and tracking.

Backing could have good results, but only do that as a last resort. Maybe its a good thing to find some restoration services, or give a call to a big radio-station. They have to deal with that stuff too, and maybe they can help you somehow.