Isn't it surprising that it is so difficult to find example ab1 files on web. Perhaps all those old ab1 files from human genome sequencing suffered digital decay over the last decade.

You can get data in SCF format from NCBI trace archive. For example: http://www.ncbi.nlm.nih.gov/Traces/trace.cgi?cmd=retrieve&val=4-10

Then use the "Save query" result button (put a check mark against the SCF box) to download a file with the data in SCF format.