What to do if you are stuck with a file with non-printable ASCII characters. Well, you normalise the content, by either removing or converting unwanted characters.
What to do exactly depends on the input source (what's wrong with the file, if that is known) and the desired output.
File contains control characters
Example: a file with NULL characters:
Example: a file with a Byte Order Mark (BOM):
tr -cd '\11\12\15\40-\176' < syseeprom.txt > cleansander.txt
File has unknown (non-UTF-8) encoding
Unwanted line endings
Example: NFD normalized
Example: Non ascii characters