Both .ass and .890 files may be found as subtitles for videos and both of these can be converted to various other text subtitle file types. So with programs like the Subtitle Workshop you can easily perform ASS to 980 conversion.
Convert Advanced SubStation Alpha subtitles to Cavena subtitles file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert ass to 890 on Windows
A free subtitle editor
Convert from ass file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.