Data Errors In File After Write?

I am having problems writing correct data to a file. I create a string of characters (approx 5000 bytes long). The string is a mixture of text characters and numbers converted to bytes. I then:

a) write the string to a readable text file

b) display the string contents to the console

c) write the string to a file - BDF.bin (I tried both IO.BinaryWriter and IO.StreamWriter but get the same error)

The byte pattern for the text readable file and the data displayed on the console match and for the most part , data bytes in the StreamWriter file are correct (first 4096 bytes are OK) but there are some extra bytes and some wrong bytes.Here is a comparison of byte patterns (hex values character written to the file) starting at byte 4096

Console: 45 44 52 31 00 00 00 00 01 00 00 00 90 01 00 00

Binary File: 45 44 52 31 00 00 00 00 01 00 00 00 C2 90 01 00

The byte patterns match, however in the binary file, there is an extra byte (C2).To display the console data, I read one character at a time from the string and display it using hex(asc(mid(string,i,1)))I view the binary data in the BDF.bin file using a hex editor program. I even tried 2 other hex editors and all showed the same byte info.