If it has a conexant processor, there is no jtag program for it
and you won't find a full jtag size dump.
Conexant .stb files are over 900k, the usual sti5518 based .stb
files are slightly more than 700k.
If you expand the .stb file to bin with the program stbsplit, you
will see the word conexant near the beginning of the file using
a hex editor.
If it has a sti5518 processor, you can jtag dump the defective
flash and piece together a working jtag size dump with the
expanded .stb file.